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Can you explain this brake caliper position?

3K views 16 replies 10 participants last post by  ssmike 
#1 ·
Hi all,
I'm asked this all the time on my 1988 Miyata Valley Runner MTB. "Why is that rear brake down there?"



I'd love to find someone that knows the actual reason why Miyata chose the design, but speculation is welcome too. The bike was originally equipped with Exage class components, Biopace I rings at 18 speeds. That's mostly been changed to 9 speed XT/LX and some Performance Bike parts. I now have v-brake in the front but there was nothing I could do about the rear. The bike is my daily commuter.

Tnx, Glen
 
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#2 ·
It's basically there because the early (mainly Marin) guys were using roller cam brakes which fit on the same posts as that there u-brake. Roller cams are very powerful and very capable of flexing the stays. Mouting rollers on seat stays is possible but you can lose brake performance due to the flexing of the smaller diameter and longer seat stays. Chainstays are shorter, larger diameter and provide a better brake mount location to get the best performance out of the roller cam - regardless of what folks might say about mud collection. At the time your bike was made, u-brakes were a popular rear brake and in fashion .

Roller cams are not the easiest in the world to set up and Suntour had licensed WTB's roller cam design so when Shimano made their brake to fit on the roller cam boss, viola - the u-brake. (Anyone out there remember which came first - the Dia-Compe 990 or the Shimano U?)

This is a topic that could consume reams of conversation. At the time there were two very distinct camps on brakes - the Mountain Bike Action types with cantilevers and the old schoolers who favored rollers. A similar questions might by "why is your rear derailleur cable routed under the bottom bracket?"

So that could be one answer. I really like how they clean up the seat stays and with all the cables under the d/t, the bike - to me - is just clean sans any cables on the t/t.

Next?
 
#4 ·
Blame it on Richard Cunningham. He put a set on the underside of a Mantis, and on the Nishiki's he was designing, and POOF...everyone copied him. Well, almost everyone. GT and Rocky Mountain and several others put them on the seatstays but most brands went under the chainstays. GT's and Rocky's usually got away with it as the former with their triple-triangle design actually had pretty short seatstays (plus they were reinforced by joining the seattube and the toptube only a couple inches ahead of the brake studs), and Rocky was a big used of wishbone seatstays so again, shorter than other companies with fastback stays.
 
#6 ·
I think Mike's answer is spot on. The chain stays flex less than seat stays, so the brakes work better there than on the seat stays.

And the best question of all, "Does your rear derailler cable really pass through the brake boss? And if so, how does it get around the brake bolt?" That's a slick looking set up, but I'm not sre how it works.

I agree that it looks really clean, but it also is a pain in the butt when it comes time to take the rear wheel off on the side of a trail.
 
#7 ·
Understay brakes worked very well but clearance was bad in real muddy conditions.There was a lot of chain suck too.Shimano came out with the Shark Fin for their u-brakes.
Diacomp came out with the u-brake first,for the earlier BMXs,when Freestyling was around during the early eighties I think but don't hold me to that.
You can run v-brake levers with a u-brake.I set up one of my Haros with an Odyssey u-brake in the rear,Shimano Vs up front hooked up to Servo-Wave levers. A lot of BMXs run u-brakes from Odyssey and Diacomps and these will fit the u-brake bosses on the older mountain bikes.You can run up to 26x2.0 tires. Easy to center and adjust and no problems removing the rear tire out in the field.The brake cables run thru the bosses on some bikes like the Haros.
I like the XT version myself.
 
#9 ·
laffeaux said:
And the best question of all, "Does your rear derailler cable really pass through the brake boss? And if so, how does it get around the brake bolt?" That's a slick looking set up, but I'm not sre how it works.
The rear derailleur cable routs through the boss on both my Salsa and Ibis. The bolt doesn't thread into the base part - only into the post part.
 
#10 ·
Yup that's U-brake, I'd guess a Dia Compe based on the color. Mike is spot on with his reply. My 1st mtn bike (steel a 1987 23" Trek 830, I thought mtbs were supposed to fit like road bikes) had/still has a silver Shimano Deore U brake down there. Good brake, lasts forever. Only complaint I had was in loss of braking power in muddy conditions as it takes a heavy spray from the rear wheel. You should see the giant moto brake levers on that beast, I swear they we supposed to double as bash guards, made for a nice combo with the Deore (pre XT) 6 speed thumbies.
 
#12 ·
Thanks much for all the comments

I checked in this morning to find a wealth of information about my bike's strange brake position! I found the link to the old Cunningham Indian especially interesting.

Here's a pic of the Miyata in it's original form. (plastic pedals and all) The big 28/38/46 Biopace front rings with 14/30 rear made this bike a difficult hill climber, which I happen to be surrounded by. But the smaller head angle and long front wheel rake makes this bike very stable on the road. It's the first thing someone not familiar with riding the bike will notice on their first turn. It's almost like the headset is binding to them... The bike came with dense foam grips (much like a Grab-on foam MTB grip) but bigger diameter. I'd love to find a similar pair. It really helps with my carpal tunnel.



Thanks Banks for the brake pad recommendation. I like Built4Speed put V-brake levers on this bike. Since I changed the front brake to V-brake, I wanted the brake levers to match. I couldn't use the U-brake levers with the new front, it didn't pull enough cable. So stopping with the rear takes considerably more effort.

Thanks again for the comments,

glenk
 
#13 ·
Changing rear wheels is a pain!!

Yes Laffeaux you hit it right on. It is very cumbersome to change the rear wheel. You have to compress the brakes together while trying to slide the axle onto the frame and pass the rear derailleur. It doesn't help that my new rear hub is 135mm vs the original 130mm width. I now have to spread the chainstays apart along with doing the above. But this Miyata was a beautifully built frame and it was such a waste not to use it. The bike just hung in my garage all the time because of its original limitations.

Regards,
glenk
 
#14 ·
To solve your brake/ brake lever matching problem, you could stick with your old u-brake levers, and run an eccentric pulley on the v-brake. Problem Solvers makes them, they replace the noodle on your v-brake with an eccentric pulley which changes the leverage of the brake such that a normal u-brake lever will pull enough cable.

Another thing you could do would be to run LX v-brake levers, and put them on the max leverage setting, which results in a leverage ratio similar to that of a u-brake lever.

Also, Avid used to make a set of brake levers which would work with u-brakes and cantis, but which also had an adjustable leverage feature which let you run them with a v-brake, too.
 
#16 ·
A bit off topic but...

I remember back when i was young, the freestyle bmx guys running brakes on both the chain and seat stays, or on the seat stay with a foot (backpedal thing) brake. that and a brake on the backside of their forks. so they could do all those tricks that i could never ever figure out how they even thought it was possible!!
 
#17 ·
mik_git said:
I remember back when i was young, the freestyle bmx guys running brakes on both the chain and seat stays, or on the seat stay with a foot (backpedal thing) brake. that and a brake on the backside of their forks. so they could do all those tricks that i could never ever figure out how they even thought it was possible!!
And after all these years, the 990 is still the brake of choice. There's more u-brakes being used today on freestyle bikes than there ever was on mountain bikes.
 
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