Component Problems On New Sport Tourer

[Sandy]

I had a road tourer bike built as I wanted to have the option of larger tires (700x32 on the bike at present), and wanted a greater top tube slope (5 degrees), and an increased trail. I decided to use a carbon fork which necessitated the use of a cross fork. I chose TRP CX8.4 brakes over cantilever as, per my understanding, they stop considerably better and have excellent modulation. I knew the pad/rim clearance would not be great. In addition, I was told that the problem of brake/fork shudder on the cross fork should be minimized with the TRP CX8.4 mini v brakes. I am using mostly Shimano 7900 Dura-Ace/Deore XT 10 speed components.

I have ridden the bike very little, for multiple reasons, since I purchased it (250 miles). However, I have determined several problems, two being most significant to me. I would appreciate GREATLY, any help/suggestions you give me.

Problems:

1. When I rode down a hill and applied the front brake, at speeds as low as 17-18 miles per hour, I would feel a very significant vibration...in the entire front end of the bike....I assume that is a cross fork/ brake shudder. It was highly disconcerting. The shop that built up the bike said it is fine, but they did not ride it down a hill, I am sure. Any solution to the vibration? If it is indeed fork shutter, what can be done to lessen or eliminate it? Anything else it could be?

2. The TRP CX8.4 brakes have remarkably small pad to rim clearance, and if a wheel is not in perfect true, I would anticipate a brake pad /rim rub.Can the brakes be adjusted to increase clearance without causing the brake shifters to almost touch the handlebar while applying the brakes? How does one maximize pad clearance safely, please?

3. The rear brakes squealed loudly in stopping after going down a hill at about 25+ mph. Solution?

4. The 7900 ST shifters seem much wider at the base than the 7800 I use on my steel Serotta CDA, and although I am using the identical handlebars as on my CDA , I ride mostly on the hoods and sometimes felt the handlebar seemed too wide at the hoods. Solution?

5. Unlike the 7800, there seemed to be significant force needed to shift the 7900 front derailleur going from the small (34) to the large (50) chainring. Is this a 7900 problem? Solution, please?


Thank you ...thank you... for any suggestions you may have ....other than taking up checkers instead of cycling.


Shuddering Shaking So Sad Sandy

[Peter P.]

You've got a compatibility issue with the 7900 levers vs. the cantilevers. If you had levers that moved more cable then you could set up the brake arms with more clearance. Mini-V's, and V-brakes in general, can be used with road levers but require close pad setup. That's one reason they're not standard fare in cyclocross racing, lack of mud clearance.

You could try adding a Problem Solvers Travel Agent to boost the cable movement, allowing you to readjust your brakes with more pad clearance.

Or, you'll just have to go to standard cantilever brakes.

To address the brake squeal and shudder, first verify that you've toed-in your brake pads. The end of the brake pad toward the front of the bike should contact the rim before the trailing end. The easy way to do this is to put a credit card under the trailing end of the pad while the mounting bolt is loose and you're squeezing the brake lever, forcing the pads against the rim.

If that doesn't work, try to sand the pads with some 150-220grit sandpaper to take off the gloss. If that doesn't work, try a different pad combination. You may need to do the sand the rim sidewalls in extreme situations. It's sometimes easier to do this while riding the rollers or at least with the rear wheel on the trainer. Just scoring the rim surface is good enough.

No. 4+5, I can't help you on.

[christian]

1). Either the headset is loose, or you brakes aren't torqued sufficiently, or the pads are poorly adjusted. Mini-vs should not do that.

2). That's a function of mini-vs. nothing to be done.

3). Pad adjustment or pads glazed over. I think 8.4s have hemispheric adjustment, so fiddle with them a bit to make them toe-in.

4). Nothing to be done.

5). Should not be so, could be a function of cable-routing but it shouldn't be a big issue. I'd have the shop look at it.

[AngryScientist]

couple things:

-first, on the front end, make sure the headset is nice and tight, any play in the headset preload WILL cause a font end shudder under heavy braking.

-for cross forks, i've found PAUL brakes to be the absolute gold standard, if all else fails, consider a pair of paul brakes for the front end:

https://s3-us-west-1.amazonaws.com/paulcompimg/products/minimoto_1_main.jpg

-toe-in; make sure, both front and rear that you've got a decent amount of tie-in on the brake pads, that goes a long way towards quieting down noisy brakes.

-the hood shape is just different on 7900 from 78oo, not much can be done about that.

hope some of that helps!

[AngryScientist]

and christian types faster than me.

[oldpotatoe]

I had a road tourer bike built as I wanted to have the option of larger tires (700x32 on the bike at present), and wanted a greater top tube slope (5 degrees), and an increased trail. I decided to use a carbon fork which necessitated the use of a cross fork. I chose TRP CX8.4 brakes over cantilever as, per my understanding, they stop considerably better and have excellent modulation. I knew the pad/rim clearance would not be great. In addition, I was told that the problem of brake/fork shudder on the cross fork should be minimized with the TRP CX8.4 mini v brakes. I am using mostly Shimano 7900 Dura-Ace/Deore XT 10 speed components.

I have ridden the bike very little, for multiple reasons, since I purchased it (250 miles). However, I have determined several problems, two being most significant to me. I would appreciate GREATLY, any help/suggestions you give me.

Problems:

1. When I rode down a hill and applied the front brake, at speeds as low as 17-18 miles per hour, I would feel a very significant vibration...in the entire front end of the bike....I assume that is a cross fork/ brake shudder. It was highly disconcerting. The shop that built up the bike said it is fine, but they did not ride it down a hill, I am sure. Any solution to the vibration? If it is indeed fork shutter, what can be done to lessen or eliminate it? Anything else it could be?

2. The TRP CX8.4 brakes have remarkably small pad to rim clearance, and if a wheel is not in perfect true, I would anticipate a brake pad /rim rub.Can the brakes be adjusted to increase clearance without causing the brake shifters to almost touch the handlebar while applying the brakes? How does one maximize pad clearance safely, please?

3. The rear brakes squealed loudly in stopping after going down a hill at about 25+ mph. Solution?

4. The 7900 ST shifters seem much wider at the base than the 7800 I use on my steel Serotta CDA, and although I am using the identical handlebars as on my CDA , I ride mostly on the hoods and sometimes felt the handlebar seemed too wide at the hoods. Solution?

5. Unlike the 7800, there seemed to be significant force needed to shift the 7900 front derailleur going from the small (34) to the large (50) chainring. Is this a 7900 problem? Solution, please?


Thank you ...thank you... for any suggestions you may have ....other than taking up checkers instead of cycling.


Shuddering Shaking So Sad Sandy

Fder effort, compared to 7800, is partially due to under the tape der. Housing vs in the breeze, der housing.

Using a roller? Top tube cable routing, down around roller for fder routing? Effort is going to higher. Helps a little to use 5mm der housing(better for Rder also) and route housing behind handlebars.

[Sandy]

I genuinely appreciate the very helpful suggestions/solutions. I had clearly mentioned to the shop who built up the bike about toe-in but the shop mechanic said it was not necessary. I had, prior to purchase of the brakes, spoken extensively to both TRP and Paul Component Engineering. I will remember the Paul recommendation.

I am going to ride try to find someone who is really competent and have the mini v brakes set up optimally. Your suggestions will be followed.

Not a mini thank you, but a very large one,


Squealing Shuddering Shaking Stopping Sandy:banana: