Gearing questions - specifically about putting larger cassettes on road bikes.

Discuss light weight issues concerning road bikes & parts.
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alcatraz
Posts: 588
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Hi WW.

I recently started exploring putting larger 11-36t cassettes on road bikes, and I've also seen many youtube so called "hacks" to go beyond the specified range of a road bike.

What confuses me is this table here that shows the pitch of a cassette. It says that for 11s cassettes, mtb and road have different cog pitch. An MTB cassette wouldn't index right on a road bike then, right?

What about all these fancy 1x sram systems for road. They seem to use some of the same cassettes as they offer to mtb. A cassette series is called PG1130 that can go all the way from 25t to 36/42t. When does this cog pitch difference then take place and shoudn't the cassettes have different model numbers?

    Cassette Sprocket Pitch Code Sprocket Thickness Spacer Thickness Stack Width
    mm. mm. mm. mm.
    Campagnolo 10-speed 4.15 C10 1.7 2.42 38.8
    Shimano 10-speed 3.95 S10 1.6 2.35 37.2
    SRAM 10-speed 3.95 S10 1.6 2.35 37.2
    Campagnolo 11-speed 3.85 C11 1.6 2.25 40.1*
    Shimano 11-speed 3.74 S11 1.6 2.14 39.0*
    SRAM 11-speed 3.72 na na na na
    Shimano 11-speed mtb 3.9 na na na na
    SRAM 11-speed mtb 3.9 na na na na

I have a an old 10s sram red derailleur (max 28t). I recently obtained a "road link" and I'm interested in shelling out big cash for a sram XG1099 cassette 11-36t. Seems 10s doesn't have this difference in pitch. Can someone confirm?

My friend has a sram PG1130 11-36t cassette on his road bike with a shimano ultegra 6800 mid cage derailleur and it seems to work fine. Is this an erroneous pitch match or what?

/a

pdlpsher1
Posts: 1337
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

11 speed MTB cassettes have the same pitch as 11 speed road cassettes. The difference is that 11 speed MTB cassettes can fit on both a 10 speed MTB hub or a 11 speed road hub when fitted with a spacer. To run a 11 speed cassette you must have a 11 speed derailleur and shifters.

The RoadLink will drop the pulley of a derailleur so you can run a larger cog. But a RoadLink doesn’t increase the wrap capacity. So if you decide to run a 11-36 cassette, make sure your derailleur has enough chain wrap capacity to handle your gear combination. If you disregard the chain wrap capacity you run the risk of damaging your frame if you accidently shift into the big big combination.

The new Shimano Ultegra rear derailleur is designed to handle a 11-34 cassette without a RoadLink, and it has enough chain wrap capacity to handle the typical front chain ring setups.


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Last edited by pdlpsher1 on Fri Nov 03, 2017 1:11 am, edited 1 time in total.

by Weenie


alcatraz
Posts: 588
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Thanks for that...

This would be my observation as well. But I can still not understand the details. For example why does the table then show a difference of 3.9mm on mtb vs 3.72/3.74 for road? Are the numbers bs or what?

I just measured a 36t pg1130 and my slightly inaccurate measurement is a pitch of 3.8mm. Might be 3.72mm plus some dirt come to think of it. Can I then conclude that this is a road pitch cassette?

At what point does the pitch become 3.9mm like in the table?

Also does this have to do with road hubs being 130mm and mtb hubs being 135mm?

/a

PS. No worry about chain wrap/slack capacity. I can easily switch the big chainring from 50t to a 46t.

TobinHatesYou
Posts: 621
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

I thought the R8000 medium cage was officially designed for up to 11-34t. That basically means it'll unofficially support 11-36t though.

addictR1
Posts: 1220
Joined: Sun Jun 10, 2012 1:11 am

by addictR1

Interesting to see how you like the roadlink


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TobinHatesYou
Posts: 621
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

addictR1 wrote:Interesting to see how you like the roadlink


It makes the range of acceptable indexing a lot smaller and some people can never get perfect shifting into the smallest cogs, but it "works."

pdlpsher1
Posts: 1337
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

TobinHatesYou wrote:I thought the R8000 medium cage was officially designed for up to 11-34t. That basically means it'll unofficially support 11-36t though.


Thanks for the catch. I meant 11-34 and not 11-36. I corrected it in my post.


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pdlpsher1
Posts: 1337
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

TobinHatesYou wrote:
addictR1 wrote:Interesting to see how you like the roadlink


It makes the range of acceptable indexing a lot smaller and some people can never get perfect shifting into the smallest cogs, but it "works."


On my tandem I’m running an Ultegra 8000 GS derailleur, on a XT 11 speed 11-40 MTB cassette, with perfect shifting across the entire range. And with plenty of chain wrap capacity to run both the small/small and big/big gear combinations, with the B-screw pushed in almost all the way. BUT this component combination may not work on other bikes. This is because my tandem has very long chainstays, probably 44-45cm long. The front chain rings of my tandem is 50/34.


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Last edited by pdlpsher1 on Sat Nov 04, 2017 7:09 am, edited 1 time in total.

pdlpsher1
Posts: 1337
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

alcatraz wrote:Thanks for that...

This would be my observation as well. But I can still not understand the details. For example why does the table then show a difference of 3.9mm on mtb vs 3.72/3.74 for road? Are the numbers bs or what?

I just measured a 36t pg1130 and my slightly inaccurate measurement is a pitch of 3.8mm. Might be 3.72mm plus some dirt come to think of it. Can I then conclude that this is a road pitch cassette?

At what point does the pitch become 3.9mm like in the table?

Also does this have to do with road hubs being 130mm and mtb hubs being 135mm?

/a

PS. No worry about chain wrap/slack capacity. I can easily switch the big chainring from 50t to a 46t.


I don’t know where you got the pitch numbers but all Shimano 11 speed cassettes have the same pitch no matter if it’s for road or MTB.

All 11 speed MTB cassettes are made such that it’s compatible with either a 10 speed or a 11 speed hub. This is accomplished by making the cassette carrier shorter so it can fit on a shorter 10 speed hub. Because of the shorter carrier, the largest cog is actually positioned beyond the end of the carrier. This is OK because the large diameter of the largest cog on a MTB cassette is so large that it won’t interfere with the spokes. To fit a 11 speed MTB cassette on a 11 speed hub you must also use an included spacer. Otherwise the cassette carrier will be too short. Some road cassettes are actually designed like a MTB cassette, namely the new Ultegra 8000 11 speed 11-34 cassette. One can use this cassette on either a 10 speed or 11 speed hub. So if one has an old wheel with a 10 speed hub, you can run the 8000 11-34 cassette perfectly without the spacer. I’m not sure if the 11-32 is also designed this way but most likely not due to lack of clearance between the 32 cog and the spokes.


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ooo
Posts: 446
Joined: Sat May 21, 2016 12:59 pm

by ooo

I have tried roadlink - it makes shifting slow.
11-32 + smaller front chainrings will do better
unless you need to stay in fast group rides

110-110 compact cranks:

50-34x11-36 = low gear 0.944, capacity 41 exceed official specs (GS=37) and specs+2 (GS+2=39)
48-34x11-36 = low gear 0.944, capacity 39 = specs+2 (GS+2=39)
46-34x11-36 = low gear 0.944, capacity 37 = specs (GS=37)

130-74 triple, minus big chainrings, plus cx chainring:

46-30x11-32 = low gear 0.937 capacity 37 = specs (GS=37)
46-28x11-32 = low gear 0.875 capacity 39 = specs+2 (GS+2=39)

Shimano Metrea road double FC-U5000-2 with stock chainrings:

46-32x11-34 = low gear 0.941, capacity 37 = specs (GS=37)
'

by Weenie


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