Tandem Cycling - Why are tandems slow climbers? (In General)

Ok before I start a flame fest here I am talking "IN GENERAL". I know there are some teams that can climb quite well because I ride with one frequently. Also I am not trying to insult anybody I am just trying to understand.

For sake of comparision if you compare your average single rider to your average tandem team climbing up a good size hill the single (seems to) always win. Why is that?

From the archives: http://www.bikeforums.net/showpost.php?p=49147&postcount=11

Teamwork/ability/inertia

Tandems behave differently than singles. For one thing, momentom lost on a tandem is much harder to regain. Once a climbing speed is arived at, it's hard to climb faster. Most teams cannot just stand up and start pounding a huge gear up a hill like can be done on a single.

That being said, in my limited experience I have found that the tandem climbing rate is usually about mid way between the ability of the two riders.

Tandems behave differently than singles. For one thing, momentom lost on a tandem is much harder to regain. Once a climbing speed is arived at, it's hard to climb faster. Most teams cannot just stand up and start pounding a huge gear up a hill like can be done on a single.

That being said, in my limited experience I have found that the tandem climbing rate is usually about mid way between the ability of the two riders.

Two very valid points amongst probably quite a few. On top of that you have to have an experienced team that works. The gear chages are generrally a factor aswell. I know that On a single,I am up and down the gears, according to energy level, terrain and leg strength. On a Tandem You start off in a high gear and go down, very rarely do we change back up to a higher gear again, even though cadence may go up a bit on certain parts of a hill.

Why worry about hill speed though, providing you can get up them. On the flat, when you wind it up it is so easy to maintain a high speed without a great deal of effort, and the downhills are only slowed down by how loud the stoker can scream.

Ok before I start a flame fest here I am talking "IN GENERAL". I know there are some teams that can climb quite well because I ride with one frequently. Also I am not trying to insult anybody I am just trying to understand.

For sake of comparision if you compare your average single rider to your average tandem team climbing up a good size hill the single (seems to) always win. Why is that?

I think that it's the motor. My wife and I have been tandeming for almost 30 years. Virtually all of the tandem teams that we know are couples who choose to ride a tandem because they aren't closely matched physically. Without a tandem it would very hard for the two of them to stay very close together for extended rides.

Climbing an extended hill is essentially a power to weight issue. A tandem has essentially twice the weight of a single bike but two riders. The problem is one of those riders likely isn't as fit as the other and can't contribute as much to the climb. Tandems have twice the weight but usually don't have twice the power.

Why worry about hill speed though, providing you can get up them. On the flat, when you wind it up it is so easy to maintain a high speed without a great deal of effort, and the downhills are only slowed down by how loud the stoker can scream.

Hahaha. I told my wife (the stoker) this just before we started a fast downhill back home on an after work ride last Thursday. We had done a nice climb as well, of course, and later when I asked her if she was sore, she said, "yeah, my throat hurts!"

We wanted to bring this topic back for some time. Now we have some time... As we are sure it is obvious, English is our second language…. so please bare with us.

We read the postings in this thread and in other similar threads in the past. We believe there is one factor that may have been mentioned and we missed it and that makes some tandem teams slower in the hills. One way to describe this factor could be: "differences in power output during the stroke cycle" This idea came out when someone was talking about OOP and how his stoker tended to "stop" the pedals at 6:00/12:00 o'clock…. if we understood right. Is there a way to test this?

Although we are not matched perfectly, both of us can climb faster on our singles than we do in the tandem. It is the long, 5 to 10 % hills, where we loose the most ground to single riders. Surprisingly in the really long and steep >10% climbs we do comparatively much better. This fact, made us think that frame flex may not be a big factor for us. We have tried high cadence. We have been spinning on a fix gear stationary to smooth our stroke for at least three hours a week for more than a year. We both wear HR monitors.

We live near the foothills of the Sierras in the Central Valley of California and we want to climb as efficiently as we can. Any ideas or feedback will be greatly appreciated.

I concur with this analysis following a recent trip to the Pyrenees. We were able to ride <5% hills as fast or quicker than many solo bikes, 5-10% we were much slower than the solos.

Having riden 10-25% hills on a tandem and solo bike in the UK I fine the limiting factor is gearing options.

It is certainly harder to anticipate hills of a tandem and get out of the saddle in advance - very tough for the stoker I suspect. This would certianly contribute to the loss of momentum.

One options is probably to cycle areas that have steep hills rather than long 10% gradients. From memory that should be possible in the Sierras.

We took our CoMo Speedster on the hilliest group ride on our schedule a couple weeks ago. We used our lowest gear (32x32 I believe) quite a bit, but we passed numerous other cyclists along the way.

On the hardest climb (~10% for .9 mile) we were between 75-80 rpms for nearly the whole way. This hill makes me cry with my 39x25 on my road bike so I’d say it was a bit easier on the tandem, but mainly due to the lower gearing.

In the end, it was a very satisfying ride, though a bit tiring :)

-murray

We took our CoMo Speedster on the hilliest group ride on our schedule a couple weeks ago. We used our lowest gear (32x32 I believe) quite a bit, but we passed numerous other cyclists along the way.

On the hardest climb (~10% for .9 mile) we were between 75-80 rpms for nearly the whole way. This hill makes me cry with my 39x25 on my road bike so I’d say it was a bit easier on the tandem, but mainly due to the lower gearing.

In the end, it was a very satisfying ride, though a bit tiring :)

-murray
My lowest gear on the tandem is 24/32 and offroad on some of our Enduro events this is just a bit too tall a gear for the more severe long climbs- the legs pump up for too long. What have found though is that short sharp hills up to about 400yards we can blast, whether offroad or on road. Longer hills we settle into a rhythm at the bottom of the hill, and just grind. The longer the hill,The more we gain on the solos, But there is no way we can blast up them. Even trying to put in a spurt from a steady pace is difficult, as momentum is not there. What is possible though is to gradually build up speed from a steady pace, and once the momentum has been gained it can be maintained. There is nothing more satisfying to us than to catch that fit solo rider that blasted from the bottom of the hill, just before the crest of the hill.

Tandems are 'generally' slower uphill 'cause they are so much faster going downhill!
Again: Teanmwork, ability, inertia!

Gee, tandems slow uphill? I hadn't noticed, but then I'm slow on my solo bike too.

Doc

Hmm, I have noticed this also. 15 years ago I would invariably drop the bunch whenever the road pointed uphill, now on the tandem with the Mrs ... like a snail.

Obviously it can't be the extra 4 stones of weight I have put on in the interim so it must be this "tandems are slower uphill" phenomonen. :)

tandems will climb just fine, particularly if the tandem team can climb out of the saddle. Tandems only seem slow on hills because they're faster on the flats. Given the aerodynamics, a tandem team of 2 equally strong riders will be faster on the flats than either rider by themself. ( 2times the horsepower, and only slightly more than 1 times the wind resistence). However, when it comes to climbing, the aerodynamic advantage becomes mostly irrelevant. So on the hill it's 2 times the power, approximately 2 times the weight, and the advantage over the single rider is lost. Thus, comparatively weaker riders on a tandem that can keep up with a stronger single rider on the flat, ut bcan't match the single rider's pace on the hill. But it's not because tandems can't climb; its because they go so well on the flats.

Climbing an extended hill is essentially a power to weight issue. A tandem has essentially twice the weight of a single bike but two riders. The problem is one of those riders likely isn't as fit as the other and can't contribute as much to the climb. Tandems have twice the weight but usually don't have twice the power.

Yup, weak stoker :D , that is what I always blame it on. But kidding aside, I really think that is it. When the comparison between tandems and singles on up and down hills is raised it is usaully on some group ride where you have a mix of singles and a few tandems. We saw it on our MS fundraiser rides. So, we get to the top of a hill and start kicking butt but then some of those same riders start to pass on the next rise.

But, who are they? Typically the strongest riders. The more average riders are a few miles back at the last sag table.

My point is simple-this comparison is usually between one strong single rider and a mismatched tandem pair. I would bet if you pitted that mismatched tandem pair agenst a more average rider, the differences would seem slight. Or if you had two equally strong riders on a tandem that fit properly.

Not to mention, some people love hills and some hate them. My ex-stoker always hated hills and all the "c'mon, honeys' would not get her too excited to try harder nor did she seem to care that all those guys were passing us. Meanwhile, I would avoid all eye contact out of shame...prefering to wait for that next downhill.

My 2cents-ck

The rest of you have said it so well. I am just recalling one of the most exciting bits of bike writing I can recall. A catagory 2 Captain (male) and a cat 3 stoker (also male) entered the Death Ride (tour of the California Alps) several years ago. The stoker was the great writer. They "Won". As in first to finish or best time or however it was figured. They could climb with just about all the racers standing and all. The captain didn't use the brakes on the descents much if at all. He ignored the stokers' screaming. Much hooting and yelling of Your are First from people going up hills. The article? in some old California Cyclist I believe. In the looooong haul the tandems start with the solo riders in the Race Across AMerica. Not as fast as the relay teams. Something about not being able to coordinate all the different body functions. Check the UMCA site for details.

Tandems behave differently than singles. For one thing, momentom lost on a tandem is much harder to regain. Once a climbing speed is arived at, it's hard to climb faster. Most teams cannot just stand up and start pounding a huge gear up a hill like can be done on a single.

That being said, in my limited experience I have found that the tandem climbing rate is usually about mid way between the ability of the two riders.

This is probably the case with us ... I'm very slow up hills and Rowan is a bit faster, but on the tandem we're about mid way.


Someone asked us why tandems didn't climb as well as singles on our ride this weekend, so I thought I'd do a search to find out. :)

We like to ride our tandem on climbing timed centuries as it adds to the challenge and for the most part we do quite well. We are good climbers on our singles and our climbing speed on the tandem is somewhere on the middle, but for both of us the tandem just feels harder to climb on if we compare it to our singles.

The statement that tandems have twice the weight and twice the power is just wrong. Yes they have twice the weight approximately (2 x each rider + 2 x solo bike) and yes both riders can try to deliver the same amount of power as they would individually, but as has been stated previously in this forum, not all of this power reaches the rear wheel. I believe that the figures given by those who have researched this factor and know more about it than I, gave the value of around 16% loss in the drive train alone for an efficient set up.

So even if both riders are able to pedal perfectly in sync (something that I believe is almost impossible as mentioned in a previous thread), and ignoring drag (come back to that) a tandem yes has twice the weight, but only about 1.8 x the total power and hence will never climb as quickly as the faster climber on the tandem as an individual.

Back to drag... Again, I thiink the figures that others have given on the increase in frontal area for a tandem over a solo is around 30% greater. So in theory, in ideal conditions (a perfect head wind or no wind at all) a tandem has around 130% of the drag of a solo and about 1.8 times the power. I don't exactly know what the equations are relating to speed, drag and power, but I do know that for a given speed, you need to deliver proportionally much more power to overcome a small increase in drag. My gut feeling is that in perfect conditions, the proportionally greater increase in power over frontal area is probably just about big enough for tandems to be faster than solos on the flat, but it's marginal in my view.

The fact that the tandem also has higher inertia also means it is less likely to slow down as much as a solo when hit by gusts which may also help in windy conditions.

However, but for an in door track, we all know that the wind doesn't hit us on the nose. I'd be really interested to find out whether anyone has looked into the increase in drag when the wind hits you side on. Having spent around 14 miles in a TT at the weekend, 7 of which climbing 1200 ft at an average of 10%, with a gale force 7 side wind, I can tell you it hurt us a lot more in terms of time lost than the solos.

I believe this theory is supported by the fact that on reasonable courses, as far as I'm aware at least, virtually all the records for TTs from 10 miles upto 100 miles are all held by solo bikes, not tandems. I know tandems are necessary raced by the top riders these days so much but if they did have such an overwelming advantage you would expect them to hold more records. If any records are held by tandems, I suspect it was on a flat course and set in very still conditions.


Certainly my experience is that we are comparatively faster to solos in very still conditions than when it is windy.

And finally back to climbing...

While it is absolutely true that any advantage a tandem may have over a solo as described above, will become less significant at lower speeds, for example when you're climbing, this does not explain why a tandem should be slower than the fastest of 2 solo riders on any given climb when compared with them riding a tandem up the same climb.

It is as some body else pointed out, all about power and weight, and as described above, the tandem does not have twice the power and so will never climb as quickly.

When you also think that both riders will never pedal in perfect sync and on a hill, when they are not in sync, even for a fraction of a second, they will be trying to carry the entire weight of the bike and riders. On a climb this affect will therefore be far more fatiguing and hence both riders will ultimately become more tired - something I think we all understand.

I would also agree with others that the most difficult climbs are the long drags around 10%. When it's really steep and everyone is in a twiddly gear, we find we can stay with solos. This could be due to the fact that on these type of climbs both riders may pedal more smoothly in the smaller gears. But it's just not possible to sustain this for long drags on slightly bigger gears. Yes, you can hold the smaller gears but then you just don't go as fast. We've often thought that we'd climb better if we had a full range of sprokets from 25 to 34 so we could pick which one is just right for our pedaling.

1) where are you getting the drive train efficiency numbers? The numbers I recall seeing are 97% efficency for a single bike (which would be the same for the stoker on a tandem), and 93% for the captain. So 4% worse than a single. Given that the Captain is only part of the power, the total efficiency loss for a tandem would be in the 1 to 3% range, depending on what percentage of the power was coming form the Captain.

2) USA Cycling National time trial records don't bear out your assertion.

For Elite men, the National 40km record is 3 minutes 17 seconds faster for the Tandem.

For Masters, both the the 70+ record, and 90+ record are faster than any of the Single Masters records including the 30+.

Its pretty clear from those records, and just simple observation that 2 strong riders on a tandem are faster on the flats than a strong single.

Otherwise, my wife, who struggles to hold 18mph on her single, and I, could not ride in group rides that are going 28-30mph for extended periods.

In my post 6 years ago, I alluded to power to weight ratios.

Now with power meters, I have data to confirm my conclusion, at least for our team. My w/kg at FTP are 3.9. My wife's w/kg are 2.3

Our team's w/kg are 3.3 (it's above the average of the two because I'm heavier than she is).

Not surprisingly we climb faster on the tandem than she does on her single, but slower than I do on my single.

And the rate we can climb at is right at what a power calculator such as kreuzotter, http://www.noping.net/english/, would predict for a single rider with an FTP of 3.3 w/kg.

I'm sure there are small drivetrain losses, and cooridnation issues with the tandem.

But in our experience a tandem team that works well together will climb right at where ther combined power to weight ration predicts.

I can't remember exactly which thread I got this figure of 16% in loss of power in the drive train but I am pretty sure it was something like that. I remember because it surprised me.

As far as the US records sited, I would simply ask on what courses and under what conditions were these records set. I know a couple of riders in the UK road a 25 mile in about 43 mins a couple of years ago but when you look at the course, it was virtually all down hill.

And just to be clear, I'm not saying that tandems do not have an advantage as a result of a proportionally greater increase in power than drag. I am however saying that this affect is far less than many would suggest, even under perfect conditions, and is marginal, in less than ideal conditions.

Found the transmission loss data I was thinking about. http://www.bikeforums.net/showthread.php/422780-Power-loss-in-transmission?highlight=

Forum poster asu_gt did testing the lab with power meters and got a 1.8% loss for the stoker (consistent with a single bike) and 6% loss for the Captain, although that loss dropped as low as 4.5% with both riders pedaling, indicating an efficiency loss overall for the tandem around 4%, compared to 2% for a single bike.

At time trialing speeds, that's going to be overwhelmed by the aerodynamic advantage.

As for the U.S. records I think they all come from Nationals, although I could be wrong. http://www.usacycling.org/forms/records.pdf they usually try to have as flat of course as possible to make times comparable.

Interestingly for the Elite male records, the single and tandem records are both held by John Frey. (with Rod Bush on the tandem)

So if you asssume Bush is about as strong as Frey that gives you a good idea of the relative tandem advantage.

On his single, Frey could "only" do 31.5 mph. On the tandem they managed 33.8mph, which is a pretty huge difference at those speeds.

In my post 6 years ago, I alluded to power to weight ratios.

Now with power meters, I have data to confirm my conclusion, at least for our team. My w/kg at FTP are 3.9. My wife's w/kg are 2.3

Our team's w/kg are 3.3 (it's above the average of the two because I'm heavier than she is).

Not surprisingly we climb faster on the tandem than she does on her single, but slower than I do on my single.

And the rate we can climb at is right at what a power calculator such as kreuzotter, http://www.noping.net/english/, would predict for a single rider with an FTP of 3.3 w/kg.

I'm sure there are small drivetrain losses, and cooridnation issues with the tandem.

But in our experience a tandem team that works well together will climb right at where ther combined power to weight ration predicts.

I agree 100%. I don't have hard data except on known climbs we are right where I would predict from our single bike speeds. Much slower than you but still where I would expect it too be.

Wayne
Remember slower riders work just as hard and do it longer than fast riders.
Slow riders that go hard unite!

Thanks for the reference to that thread on power loss. Can't think where I got 16% from. I think I'm going senile.

Nevertheless, this still doesn't change my personal belief that the advantage is much less than has been suggested.

Indeed, it suggests to me at least, that the fatiguing effects of riding a tandem described both in this thread and the thread on power loss is actually greater than I previously had thought

And this effect is exaggerated when climbing as there is a larger component of the weight of the bike and riders throughtout each pedal cycle than as there is on the flat.

Maybe an interesting question to ask is whether there are any tandem riders who feel they can climb the long draggy climbs with gradients around 10% better on a tandem than on their solo?


.

Thanks for the reference to that thread on power loss. Can't think where I got 16% from. I think I'm going senile.

Nevertheless, this still doesn't change my personal belief that the advantage is much less than has been suggested.

Indeed, it suggests to me at least, that the fatiguing effects of riding a tandem described both in this thread and the thread on power loss is actually greater than I previously had thought

And this effect is exaggerated when climbing as there is a larger component of the weight of the bike and riders throughtout each pedal cycle than as there is on the flat.

Maybe an interesting question to ask is whether there are any tandem riders who feel they can climb the long draggy climbs with gradients around 10% better on a tandem than on their solo?


.

I agree with you 100% once you reach really steep grades the tandem is even less efficient on climbs.

I agree with you 100% once you reach really steep grades the tandem is even less efficient on climbs.

.. and I think that is mainly due to inertia. On a solo, those really steep instantaneous grades can be overcome with a quick power surge, to maintain your overall pace. Of course you can do this on a tandem, but by the time you coordinate a combined surge, the damage may have already been done (a little more momentum gone).

In general, we climb somewhere 1/2 way between our solo bike climbing speeds, but the characteristics of the climb definitely matter. For tandems steady climbs are better, I think.

I wanted to see how the Kreuzotter Speed & Power calculator (http://www.kreuzotter.de/english/espeed.htm), which has a tandem function, estimated the climbing ability of tandems compared to singles.

Usually the rap on tandem climbing is that a tandem team doesn't climb as well as the team's stronger rider. But what if a tandem had two identically strong riders?

Chris Horner is a strong climber, as proven by his winning the ToC in general, and in particular his time climbing Sierra Road. Dan Connelly has put some numbers together (http://djconnel.blogspot.com/2011/05/chris-horner-on-sierra-road-power-speed.html) for Horner's ride up Sierra, which I can borrow for the analysis.

I plugged the numbers into Kreuzotter, which calculated that Horner would require 470 watts to obtain a time of 16:47 on Sierra Road (Connelly estimated 426). If we cloned Horner, and placed him as the stoker (http://www.flickr.com/photos/vonkaenel/5760277662/in/photostream/lightbox/) on a 30 lb tandem (2x the UCI 15 lb minimum bike weight), the Chris & Clone Horner team does better on a tandem). The pic below (http://www.flickr.com/photos/vonkaenel/5760277718/in/photostream/lightbox/) pieces together the Kreuzotter results for Chris on a single, and Chris/Clone on a tandem (http://www.kreuzotter.de/newWindow.htm). His time improves from 16:47 to 16:02.

http://farm6.static.flickr.com/5145/5760277718_94a42307ce_b.jpg

But the UCI doesn't require tandems weigh 30 lbs., and a tandem optimized to be light (http://www.bikeforums.net/showthread.php/390272-What-s-your-tandem-weigh?p=12665497&viewfull=1#post12665497)weight can weigh less than two singles. With a 21.1 lb tandem, the Chris/Clone increases its advantage a further 21 seconds, to 15.41 (http://www.flickr.com/photos/vonkaenel/5760209247/sizes/l/in/photostream/) a full minute faster than a single.

So, according to Kreuzotter, tandems climb better than singles.

You may argue that though the Kreuzotter calculator is generally thought to be accurate for singles, it hasn't been tested for comparing singles and tandems. You won't get any argument (http://www.kreuzotter.de/impressum.htm) from its designer.

I don't know what maths Kreuzotter has used to calculate things for a tandem but I would say it is wrong.
I have found that at best the tandem will climb at a speed similar to what would be expected by averaging the teams W/kg, and it can often be noticeably worse.

In the Horner example, Horner, and HornerX2, all climb fast enough for aerodynamics to still be in play, which I would think is why the model shows the tandem faster.

Take the power down to 250 watts, and the model shows a .1mph deficit for the tandem at 5.5mph, and 5.6 mph for the single.

Allo of which is pretty consistent with our team's observations, at speeds fast enough for aerodynamics to be in paly the tandem has a real advantage; At climbing speeds where aerodynamics are insignificant, the tandem climbs about as well as a single with the same w/kg, with a slight efficiency loss.

There may be a lot of other variables for amateur tandem riders. I know that I can't deal with coordinated standing up on the tandem. My stoker likes to stand and pedal sometimes, and at that time all I can do is try to keep the bike straight. If I stand while she sits, I still don't like the feeling. So, I just don't stand. But my single bike that I also ride regularly still has old-fashioned 2x7 gearing on it that forces me to stand often and maintain a decent cadence even on steep sections.

On the tandem, I fatigue the 'sitting' leg muscles continuously while the 'standing' leg muscles go unused.

We have quite a bit of power data from time climbing centuries and group rides on our tandem. At least on our case once the tandem reaches real steep grades it becomes quite inefficient. We've done the Ride Around the Bear 3 times and the Mount Laguna Bicycle Classic 2 times. Bellow you can see some the ride stats for the Bear 2010 and Mount Laguna 2011. I won't post our total watts but on the two rides we had a difference of 5 watts average and 9 watts Normalized power, the higher was on Mount Laguna Bicycle Classic. The two rides had about the same climbing, neither of them had any long real technical descending, on the Mount Laguna we did have the check points but it was only about 3 minutes total on the other hand on the Ride Around the Bear we had few stop signs and lights, one difference is the steepness of two of the climbs but mainly Pine Creek with grades of 20%. So I one would think that the times should be similar with the power being almost Identical but the times don't match.

2010 Ride Around the Bear (http://www.ocw.org/bear/Bear2010/2010BearET_r.asp)
Dist: 100.70 mi 5:20:01 total time
Power - ----- 802 W
Climbing: 9830 ft
Braking: -39.8 kJ (-0.7%)
Min Avg Max
Gravity -1979 -0.5 915 W
Speed 0.0 18.9 51.8 mi/h
Elev 1269 4934 8263 ft
Slope -7.6 -0.00 10.6 %
Cadence Average 89.0 rpm
6/12/2010 6:28 AM
62 degF; 1013 mbar


2011 Mount Laguna Bicycle Classic (http://www.adventurecorps.com/mlbc/2011/2011results.html)
Dist: 100.93 mi 5:43:51 total time
Power 0 ---- 1540 W
Climbing: 9765 ft
Braking: -71.3 kJ (-1.1%)
Min Avg Max
Gravity -2598 2.1 907 W
Speed 0.0 17.8 50.8 mi/h
Elev 3073 4573 5785 ft
Slope -13.1 0.02 19.9 %
Cadence Average 83.8 rpm
4/16/2011 6:10 AM
73 degF; 1019 mbar

I suspect the approximations for Chris Horner + Clone on a tandem given above by the calculator are based on Chris and his clone riding in perfect synchronisation throughout every pedal cycle, all the way up the climb. I cannot see how the calculator could possibly take into consideration the effects of riders working in any other way. And on that basis, the approximation is probably about right.

But in the real world, I just do not believe it is possible to ride in perfect synch with each other. Yes there are teams that ride well together and will climb pretty well on a tandem. Certainly much better than two stronger and less well matched riders as others have experienced. But does anyone really believe that they could match the exact same component of force on each pedal at each point around every single pedal cycle as the other rider for even one pedal cycle?

To me, this calculation actually emphasises the significance of this affec as you could put Contador and Andy Schlek or Chris Horner and his clone orwhoever on a tandem, and they won't climb as quickly as lesser climbers, let alone themselves as an individual.

The affect is clearly mitigated by the relative increase of power over drag and inertia on flat roads when compared to solos but I believe it is far more significant than many people, particularly solo riders, believe. And even more so now that it has been pointed out that we only loose about 7% through the drive train rather than 16%!