I never understood the reason bike manufacturers fitted mountain bikes with chainstay-mounted U-brakes back in the late 80s. I was never too impressed with one on my Diamondback Apex because it seems to have a lot of flex. Somebody please educate me on possible reason for thse brakes.
Why U-brakes?
bikerboy
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Also, it was generally a stouter place to mount a brake adding to its firmer feel.DeeEight said:
Ok, but how is the big pad clearance explained? It seemed to have more than standard Shimano cantis......
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Depends on the user setting up the brake. I've set brakes up with little clearance and a lot of clearance with the same lever feel. Its easier to adjust U-brakes since you don't have to take the casing of the tire into consideration when setting the angle your pads arc thru as they get closer to the rim sidewall. Fat tires on skinny rims bulge out more, and present setup difficulties with cantilevers.Fillet-brazed said:
My front westpine scissors brake has loads of tire clearance and a firmer lever feel than my rear westpine t.a.c. brake (with same levers and pads), because I didn't have to make any compromises on the pad arc path, and the leverage advantage of the scissors cam.
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So the U brake has the same leverage ratio as a standard canti?DeeEight said:
The same levers are used for either brake, and the same or more pad clearance with a U brake...... Based on that it should be equal or less leverage for a U brake. Did I miss something?
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Hmm, that's a great post, FB! You bring up some really great points.
I think the big thing is, in the 80's "alt materials" like alum & even carbon & ti were essentially being used as substitute materials, within a refined structure engineered for steel. Alan & Vitus come to mind. Aluminum is indeed much softer, and weaker than steel. What RC & a few others picked up on (early) was that alum, for the same weight, can produce a much larger diameter tube & a more rigid frame.
While working for a certain local company some years ago, we happened to buy a well known and popular SantaCruz framebuilder. One of the brand-transitioning projects I was involved with, was testing & analysis of their old frames, as we'd soon be taking over their production. Among other results, we watched in amazement as the BB's deflected vertically almost an inch and three quarters before reaching yeild. Just over an inch under normal conditions, which approximated a 200lb rider on a railroadtrack at 15mph. That is one hell of a lot of give in a rear end, and was deemed unsafe. By contrast, our house tubesets built into the the same frame configuration eventually yeilded at an inch, and about 3/8 at normal. The Merlin, Spectrum & Litespeeds we tested at the time were like rubber bands, but could handle a seemingly infinite cycle duration. Alum's yeild stregth isn't far off from its ultimate strength, and it's elongation capacity being short as well means your best bet is to keep the structure as well away from yeild as possible, with large large od's & sections. What a pain, that aluminum. Still, it's the lightest, next to the fiendish quagmire of engineering out a carbon lam, plus, it's cheap, and looks cool, so marketing is generally pushing for it... Alum it is.
Really though, in the end, you're right. While all these materials have quite different mods of elasticity, and therefore will offer a different feel, everything else that separates an ass from a rock plays a proportional part. Notably, spoke count & tension, seatpost length & material, and so on.
Basic stuff, yeah, I know, but this is probably the most thought I'll put into a posting online. I have work to do too! Marketing has definitely sold a lot of rotten mackerel to a lot of people with aquariums, and especially to people with bicycles looking for a fish.
Books keep people from falling for newspapers & magazines.
I think the big thing is, in the 80's "alt materials" like alum & even carbon & ti were essentially being used as substitute materials, within a refined structure engineered for steel. Alan & Vitus come to mind. Aluminum is indeed much softer, and weaker than steel. What RC & a few others picked up on (early) was that alum, for the same weight, can produce a much larger diameter tube & a more rigid frame.
While working for a certain local company some years ago, we happened to buy a well known and popular SantaCruz framebuilder. One of the brand-transitioning projects I was involved with, was testing & analysis of their old frames, as we'd soon be taking over their production. Among other results, we watched in amazement as the BB's deflected vertically almost an inch and three quarters before reaching yeild. Just over an inch under normal conditions, which approximated a 200lb rider on a railroadtrack at 15mph. That is one hell of a lot of give in a rear end, and was deemed unsafe. By contrast, our house tubesets built into the the same frame configuration eventually yeilded at an inch, and about 3/8 at normal. The Merlin, Spectrum & Litespeeds we tested at the time were like rubber bands, but could handle a seemingly infinite cycle duration. Alum's yeild stregth isn't far off from its ultimate strength, and it's elongation capacity being short as well means your best bet is to keep the structure as well away from yeild as possible, with large large od's & sections. What a pain, that aluminum. Still, it's the lightest, next to the fiendish quagmire of engineering out a carbon lam, plus, it's cheap, and looks cool, so marketing is generally pushing for it... Alum it is.
Really though, in the end, you're right. While all these materials have quite different mods of elasticity, and therefore will offer a different feel, everything else that separates an ass from a rock plays a proportional part. Notably, spoke count & tension, seatpost length & material, and so on.
Basic stuff, yeah, I know, but this is probably the most thought I'll put into a posting online. I have work to do too! Marketing has definitely sold a lot of rotten mackerel to a lot of people with aquariums, and especially to people with bicycles looking for a fish.
Books keep people from falling for newspapers & magazines.
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hmmm... suddenly I'm very off topic...
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Ya, the Vitus' and Alans are a different story, but even for Kleins they were saying it had a softer ride than a Salsa I think it was. Its been a while. I just found it interesting as its quite the opposite in magazines nowadays.flyingsuperpetis said:
Anyway, about that deflection, thats a lot of movement. So, where was the force exerted? Did you pull down on the bb, or push down on the seat tube? Interesting. Youd think with that much movement your paint would start cracking off since just the slightest bend and it crackles right off. I guess its distributed thoughout the frame.
Anyway you might enjoy this German study on fatigue resistance on dif materials. The results are not what most would expect. http://sheldonbrown.com/rinard/EFBe/frame_fatigue_test.htm
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Well, think of it this way. Imagine V brakes with arms that are say 3 inches longer than standard with just a standard V brake lever. This would be very high leverage and you wouldnt get hardly any pad clearance. It would be mushy because you could literally squish the pads by squeezing the brake lever.Shayne said:
On the other hand, imagine V brakes with arms 3" shorter than standard. Of course now you'll have to have the tire off, but anyway, this would be low leverage with a very firm feel at the lever and if your levers pulled 24mm of cable you would have 12mm of clearance at the brake pad and rim on each side.
So, lots of pad clearance is usually an indicator of low amount of leverage. Did that make any sense?
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Wow! I would never expect anyone to think that a Klein gave a softer ride that a Salsa. The 1990 Klein Attitude I had a while back was by far the harshest riding MTB I have ever been on. I had a Salsa of the same vintage and it was hands down a smoother ride. A 1987 Mountain Klein that I've ridden deffinately wasn't as harsh as current aluminum hardtails but still didn't have a ride nearly as nice as steel.
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If I ever come across the review I'll post it. It was a review of a few really nice bikes made of aluminum, steel, and ti, and I think they even had the CR-7 in there as well which was conceived by Mantis and half steel and alu. They were comparing the ride characteristics of the 4 materials at Moab. Interesting article. Ive seen similar stuff written as well back then. It was just thought of as a softer riding material then before market hype took over I guess. Of course these are all just human impressions and opinions. I heard some Germans did a study on vertical compliance and the dif between materials was very small. Thats just vertical, not lateral or torsional.Shayne said:
The 1990 Attitude, for me, felt very stout and rigid, but I felt (could be off) that at speed and when encountering hard hits that the fat but thin-walled fork actually felt softer than a steel rigid fork.... Again, its tough to really tell. Even while on the same bike some days it feels soft and some days harsh. I think a lot of it is mental, or maybe Im not very sensitive to that kind of thing........
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That wouldnt change a thing. Its still the exact same principle.Shayne said:
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You just reminded me of something. On the U brakes arm, if you measure it from the pivot to the cable attachment point you get X. Ok now measure from the pivot to the pad you get Y. Because Y is on the other side of the pivot you have to subtract that amount from X to get the actual length of the arm. So Dee Eight was saying its a longer arm, well it is, but you have to subract out the other part to get the true amount of leverage.Shayne said:
I still say the leverage of a U brake is right in the same ballpark of a canti. Otherwise they would need a different brake lever to feel/work right....
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The same levers are used because there's a straddle cable and yoke (which is acting as another lever in the equation). V-brakes don't have this extra lever and so required different brake levers. Powercam brakes have an actual steel cam (and they made different profile cams too) running between two pulley wheels on the brake arms to allow for different pad clearances and lever feels. The leverages are NOT the same between cantilever arms, u-brake arms, and powercam arms.Fillet-brazed said:
In fact, until about 1995, I can't recall ANY magazine or manufacturer ever testing how much cable pull different brake levers had.
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Fisher had the Procaliber is oversized prestige steel, the supercaliber in oversized aluminium, and the CR-7 with a front end that was aluminium and a back end of prestige steel.Fillet-brazed said:
ALL in the same model year, using sales and consumers as R&D dummies. Its little wonder the company went bust and got bought out by Trek.
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zing...
These were the pics off the old wtb website. I have a pair of suntours rollercams on a 24"/26" cannondale. Love em to peices. The wtbs I've felt were much smoother & lighter. You have to do this weird cable trick and ditch the cam to get em mounted on a trimble, on account of the tight fore/aft clearance & then the actuation ratio winds up matching a v brake... so I tried like hell to find a set of togglecams starting in 2000. One year too late. Everybody had some in 1999, no one's had em since. Mountain Transport was a little offshoot between Rick Hunter, Paul Price, Eric Koski, and Someone else at WTB... they were trying to figure out a way to bring the rollercam back for a little short-run, but as far as I could tell it never happened, and I needed the bloody toggle anyway. Wound up going discs in the end... Here are the pics...
More on the testing bit of this thread when I have the time to write it all out... might be a bit, as there's no real quick & easy way to get into it all.
These were the pics off the old wtb website. I have a pair of suntours rollercams on a 24"/26" cannondale. Love em to peices. The wtbs I've felt were much smoother & lighter. You have to do this weird cable trick and ditch the cam to get em mounted on a trimble, on account of the tight fore/aft clearance & then the actuation ratio winds up matching a v brake... so I tried like hell to find a set of togglecams starting in 2000. One year too late. Everybody had some in 1999, no one's had em since. Mountain Transport was a little offshoot between Rick Hunter, Paul Price, Eric Koski, and Someone else at WTB... they were trying to figure out a way to bring the rollercam back for a little short-run, but as far as I could tell it never happened, and I needed the bloody toggle anyway. Wound up going discs in the end... Here are the pics...
More on the testing bit of this thread when I have the time to write it all out... might be a bit, as there's no real quick & easy way to get into it all.
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No, you have to subtract to get the actual length of the leverage arm. And yes, its been a while since any school took place here.....DeeEight said:
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No you don't have to subtract. Not with U-brakes lever arms or powercam brake lever arms and not with canti brake lever arms either if you know lever theory correctly (and it appears at this time, that you do not).Fillet-brazed said:
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But I'm sure he's a swell guy.
Mostly, I only care enough to wonder who built his Klunker...
flame away...
Yep, that's what happens when Gary tries to design a product line himself... The procaliber was originally a Ritchey (later taiwanesified), the CR-7 was a Mantis xcr copy (taiwanesified), and the SuperCaliber (which I have one of), was pretty much the standard OS alum frame everyone was having made in [you gessed it] at the time. All Fisher really had to do was make sure marketing didn't blow the budget, and accounting funnelled the money into the right places. Couldn't even do that right, almost lost the whole works twice, finally did lose it completely, and after some time, got EXTREMELY lucky and was picked up on the cheap. I could go on...DeeEight said:
Mostly, I only care enough to wonder who built his Klunker...
flame away...
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