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Old 11-09-12, 04:56 PM   #101
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Porting over most everything that was on the 2007 Calfee frame I built up just this last spring. Besides the couplers (and cable-splitters of course) the other most significant unplanned change is the inclusion of a tapered 1.125/1.5" headtube, plus Enve fork w/tapered steerer and a Chris King Inset headset. I had a custom paint idea that turned out to be $2k, so opt'd out of doing that I'll start a thread for this new build at some point.

Pertaining to this Gates belt thread, I am toying with the CenterTrack belt idea to make travel life easier... instead of having to mess with cleaning, oiling and transporting a mucky timing chain. I like to keep things very clean and find it hard to do satisfactorily while on a tour. Weight-wise, coming from the 2007 frame the 9spd Sram timing chain & Shimano t-rings weighed 406+86= 492gms total, so there would be some saving with the Gates setup but it's not a huge amount (-200gms?).
The gates belt reduced the weight of our tandem by 1/2 pound and it sure is easier to clean without having to work around the messy chain.
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Old 11-13-12, 04:59 PM   #102
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Received the CenterTrack parts from PrecisionTandem (Mark). I did err on the free shipping, cost was $230 + shipping.

69T rings. 86gm/ea (x2)
belt: 108gm
---------
Total: 280gm

The matching components off our tandem (SRAM 9spd chain + 1 half-link, 2 - 2012 Ultegra timing rings) weighed 492gms. Interesting observation: the gates rings weigh exactly twice as much as the Ultegra timing rings.

Gates weight savings over our previous components: 212gms (7.48oz)

Ask me in 2.5 months how I think it works (new frame eta). For now, these are Christmas tree ornaments

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Old 11-13-12, 06:53 PM   #103
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Our scales must be pretty close as the 280 grams is the exact same weight that I recorded.

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Old 12-08-12, 06:07 PM   #104
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We got our Gates CenterTrack last week. I've installed it on the right-hand side of our tandem using the outer ring position on a pair of triple cranksets and had a couple of test rides riding the bike solo. We're using single bike cranks so that we can have 165mm cranks, and we have no need for a large chainring - our 26 - 42 ring combination plus 11-34 10-speed cassette gives us enough range for loaded touring plus unloaded, but relaxed road riding (including lots of riding in the mountains). I've discussed more details of this in this thread. Note that we're using Shimano 105 5603 cranks; I know that the non-center track belt rings do not work on the current-generation 5703 cranks because there is not as much clearance behind the crank arm, I'm not sure whether the center track rings would avoid this problem or not.

I'd tried this with the non-CenterTrack version of the belt drive, but there was not quite enough room behind the crank for it (despite flipping the ring and shaving off 0.5 to 1 mm of the ring that was behind the crank). With the CenterTrack version, it works quite nicely. I had to play around with several variations of ring spacers. In the end, the combination that worked best was about 3.5 mm between the crank and the belt-ring, the middle ring spaced 0.5mm closer to the frame, and the inner ring also spaced out 0.5 mm. The right-hand cup of the bottom bracket is also spaced out about 2.5 mm, but this is only to make the MTB front derailleur (a Shimano Deore model) swing in far enough to downshift easily, with a road FD this may not be necessary.

I'm using some extra-long chainring bolts on the rear, and the front crank is the same, except regular-length bolts can be used because there's no middle ring. Because the belt ring is not sitting on the mounting tabs, it was a bit tough to get it centered and so have the belt tension be consistent, but I got it in the end. We also have an N-Gear Jump-Stop to prevent derailments off the inside ring.
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Old 12-08-12, 11:22 PM   #105
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We got our Gates CenterTrack last week. I've installed it on the right-hand side of our tandem using the outer ring position on a pair of triple cranksets.
1. I still think it is apostasy for Chris_W to have a tandem with a double.

2. What about sixtiescycles admonishment to have the sync drive as close to the frame center line as possible, so to avoid the boom tube flex that the leverage from offset purportedly induces?

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First, while it might seem that there's not that much difference whether the timing belt is placed on the outside (Calfee) vs. inside (Paketa) of the drive chain rings, in fact it matters greatly. One of the key performance parameters with tandems is minimizing the boom tube flex under load. Lateral and torsional flex in the boom tube due to pedaling-induced forces translates directly into unpredictable handling as the front and back ends of the bike effectively "go in different directions..."

The amount of boom tube flex depends on the stiffness of the frame itself, obviously, but also the offset distance of the timing chain or belt from the frame center line...


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Old 12-09-12, 02:45 AM   #106
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2. What about sixtiescycles admonishment to have the sync drive as close to the frame center line as possible, so to avoid the boom tube flex that the leverage from offset purportedly induces?
I hadn't considered that, it's an interesting point. I believe our current belt-line is about 58mm, but I'll have to measure it when I get home. The only thing that we could do to get the belt closer would be to get rid of the spacers behind the RH BB cup; I might then need to go back to the road FD to give enough inboard movement and it would move the chainline a little, which I'm currently quite happy with. So, I think we'll leave it as it is for now, but thanks for bringing it to my attention.

EDIT: The belt-line was about 57 mm. I've now removed one of the BB spacers to make this 56 mm (and changed the FD to a road version to allow it to move far enough inboard to downshift easily). The official chainline for the FSA Gossamer and SL-K tandem cranksets on the timing-chain side is 53 mm, so I don't think our setup is going to be noticeably different than that. I also added two pedal washers behind each pedal on the non drive-side to make the pedals a similar distance from the frame's centerline.

Last edited by Chris_W; 12-11-12 at 12:52 AM.
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Old 04-11-13, 09:56 AM   #107
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Re: Inner ring mounting

On the 2013 Tetra, I was able to install the rear CDX ring on the inside of our Ultegra R603 timing side spider, leaving approx 2mm clearance from the belt to the chainstay.

The front Ultegra R601 spacing is a bit narrower than the rear (as verified by Q-factor diffs), I guess Shimano didn't think perfect timing ring alignment was needed - at least for typical chain setups. So, I mounted that CDX ring on the outside of the spider and then shifted the EBB by 2mm to the driveside. The timing ring alignment is still out by approx 1-1.5mm, but with the CDX setup this appears to be tollerable.

Besides the purported benefit of having the timing load moved as close to the centerline as possible, another more trivial benefit is that the crank magnet for the Garmin sensor now has plenty of clearance between it and the belt.

Here is a shot of the rear ring/belt clearance achieved:

* note the little piece of frame saver tape on the chainstay. It's there as a wear indicator just in case any rub occurs... like when riding in wet, mucky conditions when grime buildup can occur. I may remove this once we gain more confidence there will not be any rubs on the frame.

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Old 04-11-13, 09:27 PM   #108
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2. What about sixtiescycles admonishment to have the sync drive as close to the frame center line as possible, so to avoid the boom tube flex that the leverage from offset purportedly induces?
And on a V2R that would be 29mm offset center of belt to center of frame. As pictured, it takes a bit of design and custom fab to make that happen!

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Old 04-11-13, 10:35 PM   #109
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I've not been paying too much attention to this thread, so maybe someone can fill me in.

I already have a CDC 69 tooth, and it works fine for us. Is there any reason to 'upgrade' to a CDX?

Weight doesn't appear to be a reason. The CDX pulleys each weigh 6 grams less, but the +15 grams CDX belt more than makes up for them.



Is CDX any more efficient? Will we eke out another watt?
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Old 04-11-13, 10:37 PM   #110
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As pictured, it takes a bit of design and custom fab to make that happen!

Ooooh, what is that ruler? I like the attachments!
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Old 04-12-13, 06:49 AM   #111
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I've not been paying too much attention to this thread, so maybe someone can fill me in.

I already have a CDC 69 tooth, and it works fine for us. Is there any reason to 'upgrade' to a CDX?

Weight doesn't appear to be a reason. The CDX pulleys each weigh 6 grams less, but the +15 grams CDX belt more than makes up for them.



Is CDX any more efficient? Will we eke out another watt?
I waited until the CDX was available before I changed to belt drive. From what I can tell there are some advantages:

1. The CDX will absorb a little bit of misalignment.

2. My perception is that the CDX sprockets will last longer, the interface between the belt and the sprocket has been totally redesigned and incorporates extremely good contact.

3. It also appears that the CDX sprockets will self clean better if you ride in dirty conditions.
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Old 04-12-13, 08:45 AM   #112
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And on a V2R that would be 29mm offset center of belt to center of frame. As pictured, it takes a bit of design and custom fab to make that happen!

Thanks for reminding me, I forgot to post that measurement. FWIW, ours is now at 44mm 25mm from center, but still the normal/opposite side of the drive setup... blah, blah...

Last edited by twocicle; 04-12-13 at 10:37 AM. Reason: corrected belt dist from center
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Old 04-12-13, 08:48 AM   #113
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I've not been paying too much attention to this thread, so maybe someone can fill me in.

I already have a CDC 69 tooth, and it works fine for us. Is there any reason to 'upgrade' to a CDX?

Weight doesn't appear to be a reason. The CDX pulleys each weigh 6 grams less, but the +15 grams CDX belt more than makes up for them.

Is CDX any more efficient? Will we eke out another watt?
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I waited until the CDX was available before I changed to belt drive. From what I can tell there are some advantages:

1. The CDX will absorb a little bit of misalignment.

2. My perception is that the CDX sprockets will last longer, the interface between the belt and the sprocket has been totally redesigned and incorporates extremely good contact.

3. It also appears that the CDX sprockets will self clean better if you ride in dirty conditions.
While #3 may be true about the rings, the groove in the CenterTrack belt may be more of a problem in very mucky conditions as the groove can accumulate dirt & small pebbles. Not really a concern for road tandems.

Add to the list...

4. Less belt tension required.

5. Addendum to #1... Belt will not walk off the CDX rings as it can with CDC.

6. Newer bling. Not that old school, out dated gear that everyone will laugh at.

----

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Old 04-12-13, 09:43 AM   #114
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The CDX pulleys each weigh 6 grams less, but the +15 grams CDX belt more than makes up for them.

Is CDX any more efficient? Will we eke out another watt?
The belt is the made from the exact same drum mold, but cut to 12mm, apparently adding 15g. Gates uses the same drum for both CDC and CDX belts before cutting them from the drum in differnt widths. Someone with both belts handy might weight them for us on this forum.

In terms of watts, I doubt any change. It is supposed here on the forum the tension could be reduced on the CDX since the belt can't walk off. I contend the belt tension should still be nearly as high for the teeth to ride / engage correctly with the sproket. The wedge shaped teeth could watermelon seed up on the sproket, ride high and wear more quickly at too low a tension. One might argue slightly less belt tension results in slightly less pressure on bearings and give you another watt. But I suspect the tension induced by the captain, which is far more than the tension in the belt, over rides that model.

You might also have the freedom to run the belt off center, with the front or rear closer to the frame that the other. Mine for instance is 29mm in back and just over 30mm in front. The belt remains on, while minimizing the bottom tube bending. I would not do the belt much out of aling for concern about the angle wearing funny. But a little is fine.

Last edited by Turbotandem; 04-12-13 at 01:09 PM. Reason: correct dimension
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Old 04-12-13, 09:47 AM   #115
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Thanks for reminding me, I forgot to post that measurement. FWIW, ours is now at 25mm from center, but still the normal/opposite side of the drive setup... blah, blah...
Nice! 25mm is tight to configure the BB axle and to clear the chain stay. Most frames won't allow that whether right or left drive. A typical BB is 68mm, so under 38mm (half the 68mm BB plus half the belt width) is interior to the BB. On the V2r the bottom tube has an indentation for the sprocket to pass, and the stays narrow in to a yoke at the BB (as pictured previously). How do you have 25mm with the sprocket spaced from the frame as you picture, and not indented into the bottom tube? I don't understand...

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Old 04-12-13, 10:13 AM   #116
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The belt is the exact same belt with a groove cut in to it. It would be less weight if anything. Gates is not going to remake their very expensive mold for the belt for any reason. Someone with both belts handy might weight them for us on this forum.
Here is a copy of a post that I wrote afteri received the CDX system, it appears a couple of pages back. I weighed the new belt and rings.

The new Gates Center track belt drive came today. It took less than an hour to install it and tension the belt using the iPhone app.




The Wipperman 8 speed chain weighed 426 grams and the Shimano chainrings each weighed 43 grams for a total of 512 grams. The new belt weighs 108 grams and the new chainrings each weigh 86 grams for a total of 280 grams.
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Old 04-12-13, 10:33 AM   #117
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Nice! 25mm is tight to configure the BB axle and to clear the chain stay. Most frames won't allow that whether right or left drive. A typical BB is 68mm, so under 38mm (half the 68mm BB plus half the belt width) is interior to the BB. On the V2r the bottom tube has an indentation for the sprocket to pass, and the stays narrow in to a yoke at the BB (as pictured previously). How do you have 25mm with the sprocket spaced from the frame as you picture, and not indented into the bottom tube? I don't understand...
I had a "senior moment", ie: goofed. The 25mm measurement stuck in my head as a quick alignment number I used by placing a ruler butted against each seat tube and out to the belt middle, plus the ruler marks didn't start immediately at the end. My bad. Ok, the correct measurement from center to center is 44mm. That is maybe an 8mm swing (spider arm thickness + ring thickness) from placing it on the outside of the spider.

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Old 04-12-13, 10:43 AM   #118
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Andy said, "The belt is the exact same belt with a groove cut in to it. It would be less weight if anything. Gates is not going to remake their very expensive mold for the belt for any reason. Someone with both belts handy might weight them for us on this forum."

It is not the same belt, look at the chart that Ritterview posted, the original is 10mm wide and the new one is 12 mm wide
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Old 04-12-13, 12:04 PM   #119
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It is not the same belt, look at the chart that Ritterview posted, the original is 10mm wide and the new one is 12 mm wide
Both the CDC and CDX belts are made on the same 4' tall drum and then cut from it. Interstingly, the strands are wound slightly spiraling from top to bottom of the drum, so an individual belt cut from the drum might have a slight bias when placed on the bike. With CDC you might have flipped the belt around and had it walk off or not walk off differntly. The CDX makes this issue mute. I suppose Gates has the option of cutting the belt wider or narrower from the 4' drum. Has anyone checked that with the prodcut in hand? I'll check tonight and update my responses appropriately.

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Old 04-12-13, 12:19 PM   #120
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... That is maybe an 8mm swing (spider arm thickness + ring thickness) from placing it on the outside of the spider.
8mm is a pretty good reduction. Does it feel any more stiff? I don't know how to run the lever arm calulcation for stress in the bottom tube or amount of bending. But at least in a linear way you have made an 18% improvement just by mounting inboard on the spider. If I understand structural loads correctly, I think that translaetes into greater than 20% reduction in bending. Still, I don't know at what point it can be "felt" riding.
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Old 04-12-13, 12:43 PM   #121
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8mm is a pretty good reduction. Does it feel any more stiff? I don't know how to run the lever arm calulcation for stress in the bottom tube or amount of bending. But at least in a linear way you have made an 18% improvement just by mounting inboard on the spider. If I understand structural loads correctly, I think that translaetes into greater than 20% reduction in bending. Still, I don't know at what point it can be "felt" riding.
I really do not believe that from a "practical" application standpoint that whether the C/L is at 30mm or 60mm, that it will make ANY difference in actual performance. You can calculate and come up with according to your calculations a 20% reduction in bending but in all honesty how does that apply to actual performance. If there is not some flex then the structure is too stiff and will probably break. Some flexing is good.

My first two homemade tandems from 50+ years ago were single speeds but utilized RH drive so I guess I am a very early Adopter. LOL! I only see RH drive on modern tandems as a marketing gimmick. There may be a small weight saving but really is there any noticeable gain in performance? For now we will stay with our LH drive, our triple and our 12-27 SRAM fairly close ratio cassette.

And BTW our CDX belt is 12mm wide.
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Old 04-12-13, 01:01 PM   #122
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I really do not believe that from a "practical" application standpoint that whether the C/L is at 30mm or 60mm, that it will make ANY difference in actual performance. You can calculate and come up with according to your calculations a 20% reduction in bending but in all honesty how does that apply to actual performance. If there is not some flex then the structure is too stiff and will probably break. Some flexing is good.

My first two homemade tandems from 50+ years ago were single speeds but utilized RH drive so I guess I am a very early Adopter. LOL! I only see RH drive on modern tandems as a marketing gimmick. There may be a small weight saving but really is there any noticeable gain in performance? For now we will stay with our LH drive, our triple and our 12-27 SRAM fairly close ratio cassette.

And BTW our CDX belt is 12mm wide.
Thanks for the Measurement.

Oh, there is clearly a difference RH drive. I've owned both versions of the Paketa and it's not a gimmick, our times reflect it, and you feel it right away standing on a climb. As do our friends who test do the same test even one ride at a time rather than year over year as we have.

But how much of that stiffness is from the direct load path of the right side drive to the rear wheel, and how much of that is from the tight belt line spacing I can't say. That's why I ask twocycle if he notices his 8mm / 20% change on the same bike, same side, same riders, etc. If I guessed I'd say that would be 1 millimeter or two less defelection on the bottom tube, a small number I suspect. And if he feels that or not is the question. It'd be an interesting experience to hear if that feels any differnt.

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Old 04-12-13, 01:03 PM   #123
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8mm is a pretty good reduction. Does it feel any more stiff? I don't know how to run the lever arm calulcation for stress in the bottom tube or amount of bending. But at least in a linear way you have made an 18% improvement just by mounting inboard on the spider. If I understand structural loads correctly, I think that translaetes into greater than 20% reduction in bending. Still, I don't know at what point it can be "felt" riding.
Thing is, I haven't noticed any flex in our 2013 S&S Tetra frame/fork combo whatsoever... anywhere. That says a lot, because I've had one gripe or another about the flex in every previous frame we've had.

At this point, I'm just going on the reasons posted by Paketa and elsewhere that moving the timing side further inboard is technically preferable to outboard, as may help reduce twisting forces on the BB and frame. In case with the Ultegra cranks, the optimal ring alignment is 50/50 anyway (inboard or outboard there is a little compromise either way. Inboard-rear, outboard-front actually worked out better as it required the least amount of shifting the EBB and spacers).

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Old 04-12-13, 01:33 PM   #124
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Thanks for the Measurement.

Oh, there is clearly a difference RH drive. I've owned both versions of the Paketa and it's not a gimmick, our times reflect it, and you feel it right away standing on a climb. As do our friends who test do the same test even one ride at a time rather than year over year as we have.

But how much of that stiffness is from the direct load path of the right side drive to the rear wheel, and how much of that is from the tight belt line spacing I can't say. That's why I ask twocycle if he notices his 8mm / 20% change on the same bike, same side, same riders, etc. If I guessed I'd say that would be 1 millimeter or two less defelection on the bottom tube, a small number I suspect. And if he feels that or not is the question. It'd be an interesting experience to hear if that feels any differnt.
We are probably a lot closer to DubT's power wise that Turbotandem and I think below a certain power level the regular outboard spacing is stiff enough that any improvement is not noticeable. The more power the stiffer the system must be to be stiff enough.

The direct load path of the right hand drive could be an important factor since it would limit the effect of bottom bracket flex. I think that the actual BB shell can flex in addition to any crank axle flex. In addition there should be less friction in the system if that is a factor.
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Old 04-12-13, 02:04 PM   #125
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We are probably a lot closer to DubT's power wise that Turbotandem and I think below a certain power level the regular outboard spacing is stiff enough that any improvement is not noticeable. The more power the stiffer the system must be to be stiff enough.

The direct load path of the right hand drive could be an important factor since it would limit the effect of bottom bracket flex. I think that the actual BB shell can flex in addition to any crank axle flex. In addition there should be less friction in the system if that is a factor.
For MOST teams, I do not think that it makes any difference at all in performance. I again think it is more of a marketing ploy than anything else. In order to utilize it you have to get rid of the triple or move it so far outboard that you defeat the so called performance gain by having it close to the C/L of the bike. And then in order to have a decent low gear you have to compromise on gearing and use compact type gearing with a wide ratio cassette. No thanks!

Andy do you have actual data that proves the RH drive has improved your performance. I mean objective not subjective data. Ride the old bike on the same course, same exact conditions and then turn around and ride the new bike under the exact same conditions. This type of data is extremely hard to get and often becomes subjective because of various factors. Wind, temperature, team condition etc.
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