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Installed a compact for ONE event.......

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Installed a compact for ONE event.......

Old 07-08-09, 12:28 PM
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trojanman
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Installed a compact for ONE event.......

Rode the new configuration this morning. Finding a comfortable gear was kind of quirky for about the first ten miles (rolling hills), but then I got the hang of it. I didn't change the cassette so I still had a 12 in back, but still able to pull the pace line at 30+ on the flats.

I am riding The Triple Bypass this weekend and thought it would be a nice comfort. How much nicer is a 34:25 going to be compared to a 39:25?

Picked up a cheap Rival crankset at Performance for $100 after discounts.
Curiously, one crank arm of the Rival weighed almost the same as my Dura Ace WITH a pedal still attached. The plan was to just use it for this event, but now I think I may just leave it on there. Everything seems to be working fine, without any adjustments to the FD height. I get some minor chain rub in the lowest gear, but an adjustment should take care of that......

Any recommendations for a higher end crankset? Bike has full DA and the Rival looks a little out of place. 7800 compacts seem to be hard to find.

Once you go compact..........
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Old 07-08-09, 01:20 PM
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I was against compacts when I first tried one out then quickly changed my mind back after riding one a while. In my experience setting them up and running them both for myself and many others I have found no other compacts that run and shift quite as well as Shimano ones.

I run an R700 on one bike still to this day.

Now....that being said I switched back to a full sized crank on my regular/daily/race rig and still very happy with it.

A compact in a climbing event is great.

What do you lose with a compact? Not much. I did a ton of crits last year all on my compact and I never lost because I ran out of gear if you know what I mean.

I am racing on a Rival full sized right now and I have to say I think it's a stellar crank for the $$. That said I still stick by my Shimano rec.
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Old 07-08-09, 01:21 PM
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Was a DA 7800 compact even offered? You could always do an Ultegra SL compact if you want to stick with the Shimano theme. It's a nice crankset.
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Old 07-08-09, 01:46 PM
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Originally Posted by tkm View Post
Was a DA 7800 compact even offered? You could always do an Ultegra SL compact if you want to stick with the Shimano theme. It's a nice crankset.
The closest to it was the R700.
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Old 07-08-09, 01:53 PM
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The other day I was sprinting with a buddy...37.6 mph with my compact, and not spun out. Well, at least my gearing wasn't spun out. My legs were absolutely red-lined, and they certainly weren't going to give me any more.

Some riders really need that 52 or 53 tooth chainring. I'm obviously not one of them, and I'd wager that most on this forum are closer to me than to, say, Fabian Cancellara.
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Old 07-08-09, 01:59 PM
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Originally Posted by Banzai View Post
The other day I was sprinting with a buddy...37.6 mph with my compact, and not spun out. Well, at least my gearing wasn't spun out. My legs were absolutely red-lined, and they certainly weren't going to give me any more.

Some riders really need that 52 or 53 tooth chainring. I'm obviously not one of them, and I'd wager that most on this forum are closer to me than to, say, Fabian Cancellara.
At the same time "most riders on this forum" probably don't need a 10 cog cassette - they should just learn to spin and grind interchangeably as needed.....

In the end it comes down to comfort. When I ride centuries or ultra-distance type of events I find I spin a lot more. When I race I mash/prefer a lower cadence. Just seems i can react quicker. Of course....personal preference. But that is why I like a 53 when racing now and a 50 when doing longer events.

I also picked up a 52 by mistake for a crank that was headed to my TT bike. I figured "what the heck - I'll give it a shot. i used to ride a 52 back in the 90's and wht difference is 1 tooth going to make..."

I swapped the chainring after the first ride. In TT's I REALLY like to mash.
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Old 07-08-09, 02:04 PM
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Normally, the FD should be lowered by 6mm when switching from a 53T to 50T big ring.

If you can find a NOS '08 Chorus 10 compact, it would be a great buy for $300 or less. I paid only slighty more for '09 11 speed Chorus 50/34 cranks.

The 34/25 will be a lot easier to spin up the mountains than a 39/25. A 34/25 is nearly as low as a 39/29.

Use the equivalent gear formula: 25/34 x 39 = 28.7.
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Old 07-08-09, 02:05 PM
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Here is a stupid question...I'm riding a compact but would like to switch to a full, do I need a new crankset or can I just install larger rings? Is there something special about the compact crank arms?
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Old 07-08-09, 02:10 PM
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I just purchased a R700 Shimano off of eBay and plan to install it this weekend. I live in the flat land, but I will be doing the Cycle North Carolina ride in Sept and there are some hills there.

I plan to just swap out casettes to match what gearing I need, the 12-23 for around here (west coast FL) and then a 12-30 (yes it works) for the hills. I a looking forward to see how the compact rides, I might need to tweak the casette gears to make sure I don't have any big gaps around my normal cruising speeds.

I can always go back to the 53-42 if necessary, but the compact appears to be the right solution.

Mark
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Old 07-08-09, 02:13 PM
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Originally Posted by Psimet2001 View Post
At the same time "most riders on this forum" probably don't need a 10 cog cassette - they should just learn to spin and grind interchangeably as needed.....

In the end it comes down to comfort. When I ride centuries or ultra-distance type of events I find I spin a lot more. When I race I mash/prefer a lower cadence. Just seems i can react quicker. Of course....personal preference. But that is why I like a 53 when racing now and a 50 when doing longer events.

I also picked up a 52 by mistake for a crank that was headed to my TT bike. I figured "what the heck - I'll give it a shot. i used to ride a 52 back in the 90's and wht difference is 1 tooth going to make..."

I swapped the chainring after the first ride. In TT's I REALLY like to mash.
All good points.

I guess I'm pretty much always a spinner, so the 50 works well for me in nearly every application. But particularly long distance applications, like you mentioned.
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Old 07-08-09, 02:15 PM
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When I'm stud enough to mash 39x23 up a 15 mile mountain pass or 19% cheeselandia trunk road without my knees popping out, then I'll put the old 53/39 on the bike.

Until then, Shimano R700 FTW!
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Old 07-08-09, 02:18 PM
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Originally Posted by DaveSSS View Post
Normally, the FD should be lowered by 6mm when switching from a 53T to 50T big ring.
More accurate to say: there should a 2-3mm gap (think of a 25c coin) between top of teeth and bottom of derailer cage for precise shifting.
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Old 07-08-09, 02:29 PM
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With few exceptions; A compact crank won't be able to fit a standard chainring. The location of the bolts will not be the same on the two.


Originally Posted by Tress94 View Post
Here is a stupid question...I'm riding a compact but would like to switch to a full, do I need a new crankset or can I just install larger rings? Is there something special about the compact crank arms?
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Old 07-08-09, 02:29 PM
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Originally Posted by FL_MarkD View Post
I just purchased a R700 Shimano off of eBay and plan to install it this weekend. I live in the flat land, but I will be doing the Cycle North Carolina ride in Sept and there are some hills there.

I plan to just swap out casettes to match what gearing I need, the 12-23 for around here (west coast FL) and then a 12-30 (yes it works) for the hills. I a looking forward to see how the compact rides, I might need to tweak the casette gears to make sure I don't have any big gaps around my normal cruising speeds.

I can always go back to the 53-42 if necessary, but the compact appears to be the right solution.

Mark
50/34 with an 11/23 works very well around here. 50x11 is bigger than your 53/12, and the 34/23 is almost as low as your current 42/30. And if you want lower gears when you hit the hills, you can easily swap out an 11-28, or 12-27 cassette for the 11-23.
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Old 07-08-09, 02:32 PM
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Originally Posted by trojanman View Post
Installed a compact for ONE event......
i picked one up for the maratona a few years ago, and generally slap it back on for 2 weeks a year when i go to italy.
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Old 07-08-09, 02:37 PM
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If you are strong enough to hang on a 30 mph paceline, why would you need a compact for the hills? I can't hang onto a 30 paceline but easily do a 10,000 ft century on a standard 39/25.
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Old 07-08-09, 02:38 PM
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Originally Posted by Mr. Beanz View Post
If you are strong enough to hang on a 30 mph paceline, why would you need a compact for the hills? I can't hang onto a 30 paceline but easily do a 10,000 ft century on a standard 39/25.
horses for courses.

besides - racing is not the same thing as a gran fondo, or 'event.'
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Old 07-08-09, 02:39 PM
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because drafting at 30mph does not require the same amount of effort as climbing.

and I could do 10,000 ft in a 39x25, but not at the cadence I want.
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Old 07-08-09, 03:15 PM
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Originally Posted by spinerguy View Post
More accurate to say: there should a 2-3mm gap (think of a 25c coin) between top of teeth and bottom of derailer cage for precise shifting.
Your setup info is correct, but a lot of people have no idea how much extra drop is required - it's 2mm per tooth.
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Old 07-08-09, 03:17 PM
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Originally Posted by Mr. Beanz View Post
If you are strong enough to hang on a 30 mph paceline, why would you need a compact for the hills? I can't hang onto a 30 paceline but easily do a 10,000 ft century on a standard 39/25.
That statement only makes sense if the climbs are short and not too steep. Try climbing for 25 miles or more, nonstop.

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Old 07-08-09, 03:26 PM
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Originally Posted by Scorer75 View Post
The closest to it was the R700.
I'd think the Ultegra SL compact would be a better crank than the older R700. The SL crank looks a lot better, too.

Where I ride I always found myself in the large chainring on a compact. In fact I almost never used the small ring. I switched to a standard and put the compact on my heavier training bike.

It's too bad Shimano made the decision to make the 7900 group incompatible with the 7800. I think a lot of folks would be upgrading to the 7900 crankset, especially since there is a compact available now.
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Old 07-08-09, 03:30 PM
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Originally Posted by brianappleby View Post
With few exceptions; A compact crank won't be able to fit a standard chainring. The location of the bolts will not be the same on the two.
You can get 39 and 53-tooth rings drilled for 110 BCD. See http://www.sheldonbrown.com/harris/chainrings/110.html. 53-tooth rings are expensive though!
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Old 07-08-09, 03:33 PM
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Originally Posted by Tress94 View Post
Here is a stupid question...I'm riding a compact but would like to switch to a full, do I need a new crankset or can I just install larger rings? Is there something special about the compact crank arms?
That's not a stupid question. Compact cranks have a smaller bolt circle diameter ("bcd") than standard cranks. You can keep your compact crankset and put larger rings on it. 53t/39t is what's stock on standard cranks today. Assuming you're not using Campy, look for 110 bcd chainrings (standard is 130 bcd). Here's a link to some: http://www.sheldonbrown.com/harris/chainrings/110.html

Everything else being equal, larger chainrings on a smaller crank spider will be more prone to flex, but if you're not a sprinter or otherwise putting out lots of torque, you probably wouldn't notice a difference.

Edit: KevinF beat me to it. There you go.
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Old 07-08-09, 03:34 PM
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Originally Posted by bdcheung View Post
because drafting at 30mph does not require the same amount of effort as climbing.

and I could do 10,000 ft in a 39x25, but not at the cadence I want.
That, and I'm fat (by cycling standards anyway)
Pulling weight up a 12,000 ft peak is MUCH different than pulling a paceline on the flats.


I have been climbing the passes in my 39:25 with no issues (albeit slow), but really like the idea of having some comfort gears, just in case......Plus, with all of the climbing I was doing with the std crank, I am hoping the compact will feel "easy".

I had purchased a 12-27 for my std crank, but changing to a compact was almost as easy and cost almost as much as the cassette I had bought.

I think I will look around for the r700 crank. I saw one on CL recently, but I took too long thinking about it. I think ultimately I'd like to end up with a 52/36 setup.
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Old 07-08-09, 03:51 PM
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Originally Posted by tkm View Post
I'd think the Ultegra SL compact would be a better crank than the older R700. The SL crank looks a lot better, too.

Where I ride I always found myself in the large chainring on a compact. In fact I almost never used the small ring. I switched to a standard and put the compact on my heavier training bike.

It's too bad Shimano made the decision to make the 7900 group incompatible with the 7800. I think a lot of folks would be upgrading to the 7900 crankset, especially since there is a compact available now.
The "incompatibility" of the 7900 cranks with earlier model drivetrains is greatly exaggerated. Most users would find no problem putting a 7900 crank and chain on their earlier model 10 speed Shimano bike.

Never using the small ring of a compact makes no sense. The 50T is less than one cog lower than a 53T (6%). Most users switch because they find a Campy 39/25 or Shimano 39/27 low gear to be inadequate for the hills and use the compact to gain additional low gearing.

Last edited by DaveSSS; 07-08-09 at 04:57 PM.
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