Rear caliper clearance issues

Discuss light weight issues concerning road bikes & parts.
ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

Hi all,

First time poster with a question about my most recent lightweight steel build up. As pictured weights about 17.3lbs...not light for this group, but very light for steel!

I found a sweet Taylor True Temper S3 frame and just finished swapping all my kit from my BMC onto it (Campy SR 11, Zipp 404, Enve 1.0 fork etc). I installed the calipers last, only to find that the clearance between the not-yet-inflated 25c Conti tire and the underside of the caliper is close to nothing. Additionally, the brake blocks are as high as they can go in the caliper arms and I still need a bit more room to get the pads to properly seat on the aluminum brakewall. The rear is a single pivot SR Skeleton style caliper. There is ample clearance to the seat tube and between the chainstays, it just seesm the brake bridge is super low or these calipers are odd (but never hasd issue with them on BMC and other modern carbon frames). Zero issues with front, as you'd imagine.

I'm pretty deflated, as I intended to run 25-28c on this bike. But, now I am concerned about even being able to run my current wheels and a 23c tire without having to change the calipers. So, questions:

-Is it possible the frame was purpose-built to run less than 23c tires (It's not that old, I'd say early 2000s)?
-Are there other caliper options that will address tire clearance and allow me to get the brake blocks higher?
-Certainly this isn't a wheel reltaed issue, but is there any evidence that Zipps are a smidge alrger in circumference than other wheels?

Thanks!
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jekyll man
Posts: 1394
Joined: Wed Apr 25, 2007 10:23 am
Location: Pack filler

by jekyll man

I'd be tempted to say its a combination of pretty much everything.
1- 23 was the norm even 10 years ago, so most custom builds only had clearance for them.
2- your Conti tyres may be nominally classed as 25s, but history shows them to come up big in width and height.
3- depending on how old your wheels are, the widh of the rim may make the tyre even bigger.
4- skeleton brakes dont give much clearance. Try an older one to see if it improves things.
Official cafe stop tester

by Weenie


ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

Thanks for the reply.

That addresses the tire clearance issue, but what about not having any room on the calipers to move the brake blocks up so they hit the brake track properly? This is even more concerning to me (I guess i can live with 23c).

For certain my Zipps are older and "light bulb" the 25c tires a bit (I think they are of the 19-20mm ilk). Canot afford a wider rim wheel upgrade at the moment to allow wider tires at a lower tire height, but this still doesn't address the lowness of the caliper as it relates to the brake blocks. weird!

thanks!

ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

...and as pictured, uninflated 25c tires are contacting the caliper :shock:

Any recommendations for decent but cheap 23c tires to swap on and test celarance (ones that are known to measure to their actual tire size)?

thanks

ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

one more thought.
would the addition or removal of spacing washers behind the caliper achieve anything (i.e. slightly changing the location of the caliper in relation to the curvatire of the wheel)?

sungod
Posts: 1672
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

the seatstays are radial, so if you add additional spacing it will move the caliper slightly further out, but it's not going be a huge amount

ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

thoughts on it being safe and/or possible (although sacrilegious and ugly) to instal the caliper on the inside of the rear triangle?

sungod
Posts: 1672
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

if the chainstay is radial putting the caliper the other side won't change the clearance (unless the mounting hole isn't tangential)

rear brakes don't do so much, if the pads aren't quite high enough you could trim the lower edge to prevent them hitting the the wall of the rim below the brake track

another option might be to fit an adaptor to raise the caliper, this inverted for instance: https://www.youtube.com/watch?v=H1CwFa1XiGE or make something like an inverted U that clamps to the bridge using the existing hole and has a hole in the upper part to take the brake bolt (with a central bracer to stop it deforming)

ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

Thanks. Had thoughts about a bracket to relocate caliper upwards, but was concerned about it beign strong enough to handle deflection under braking. will look around!

ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

anyone know of a "drop bolt", like the one pictured, that I could use to relocate caliper upward a bit?
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NickJHP
Posts: 122
Joined: Wed Feb 14, 2018 2:22 am

by NickJHP

You could use just a front brake (would save some weight, too). In my younger days I frequently rode fixed on the road with just a front brake. In fact, I got so used to using only the front brake that even now, many years later and on bikes with freewheel and both brakes, I still tend to use just the front brake.

Marin
Posts: 3066
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

- The brigde is slightly too low on the frame.

- Contis come up huge, Veloflex 23s and probably even 25s will fit, and will ride MUCH better.

- An additional spacer under the brake bolt will help a tiny bit.

ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

NickJHP wrote: ↑
Tue Jul 31, 2018 12:02 am
You could use just a front brake (would save some weight, too). In my younger days I frequently rode fixed on the road with just a front brake. In fact, I got so used to using only the front brake that even now, many years later and on bikes with freewheel and both brakes, I still tend to use just the front brake.
True, but in NYC I find I've needed both on MANY occasions!

ylwgto
Posts: 19
Joined: Mon Jul 30, 2018 3:29 pm
Location: NYC

by ylwgto

Marin wrote: ↑
Tue Jul 31, 2018 10:28 am
- The brigde is slightly too low on the frame.

- Contis come up huge, Veloflex 23s and probably even 25s will fit, and will ride MUCH better.

- An additional spacer under the brake bolt will help a tiny bit.
Ok, good to know about Contis. Was pondering 25c Veloflex Masters or Vittoria Corsa G+, but they are pricey...would be a bummer to buy them and have them not fit.

Thanks.

by Weenie


kode54
Posts: 1324
Joined: Tue May 23, 2006 9:39 pm

by kode54

the older eeBrakes used an eccentric centering bolt...meaning that you can move it up or down 5-6mm dependent on clearance of tire. not sure if there are any other brakesets that have that option.
- AX Lightness Vial EVO D + DA9150 + Enve SES 4.5 carbon hubs
- Parlee Altum + DA9150 + Enve SES 4.5 carbon hubs
- Parlee ESX + DA9150 + THM SRM PM + Enve SES 6.7 CK hubs
- Guru Praemio R Titanium + DA9150 + Enve 3.4 CK hubs

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