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Bottom bracket alignment, pump accuracy, cable housing, and gravel frame geometry – VeloNews.com

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Backside bracket alignment, pump accuracy, cable housing, and gravel body geometry – VeloNews.com

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Have a query for Lennard? Please e-mail him at veloqna@comcast.net to be included in Technical FAQ.

Expensive Lennard,
How can I decide if the underside bracket bores of my new carbon highway body are in alignment with one another? I’ve measured the bores utilizing dial calipers in a number of locations on either side, they usually had been inside spec and spherical. However, the brand-new SRAM backside bracket appears to have extra drag, even after a 1000 miles or so, than my earlier cracked body from the identical firm that got here with the identical kind of SRAM backside bracket. With the cranksets eliminated, all the underside bracket bearings appear superb on each bikes. Maybe the store that put in a brand new backside bracket within the new body, didn’t press it in precisely flush with the body? I’ve redone the lateral preload adjustment and eliminated and reinstalled the crankset a number of instances. I’m utilizing a SRAM RED 22 crankset which got here from my earlier, 3-year-old body.

I’ve constructed wheels, bikes, and many others. since I began racing in Nineteen Seventies whereas getting my BSME. Maybe I can purchase the Park PF30 device and take away the underside bracket and reinstall it myself. Can the PF30 backside bracket be reused?
— Jeff

Associated:

Expensive Jeff,
It actually sounds as if the bearings weren’t aligned parallel with one another, and I’ve no manner of realizing if that’s as a result of they weren’t pressed in straight or as a result of the body gained’t enable them to be. I don’t know the best way to examine if the bores are parallel with out tools that solely a machinist would have.

I’d attempt to press that BB in once more; sure, you’ll be able to reuse it so long as the bearings really feel clean to show in your hand, and a regular headset press will do the job. The Park BB30 removal tool is comparatively cheap.

If that doesn’t work, I’d set up certainly one of these Wheels Manufacturing bottom brackets as a substitute. Because it threads collectively on itself, it retains all the pieces in alignment.
― Lennard

Expensive Lennard,
As a lighter rider, I’ve been a decrease strain/bigger tire disciple for a few years now. I lastly got here to understand that whereas we’re driving and speaking, we predict we’re speaking strain however are actually about speaking about completely different pumps.

All three of my flooring pumps learn completely different pressures, and I’m positive different folks’s pumps are wildly inaccurate too, so I take advantage of a Schwalbe Digital Gauge, which I’m inclined to imagine greater than varied pump strain gauges, however I ponder if all that does is give me a fourth studying. Which one ought to I imagine? How can I reliably learn my pumps’ gauges?

Ought to I cut up the distinction or common them, can I add a fudge issue, or can I calibrate the gauges?
Would the discrepancy be linear; that’s, if the pump reads 10 over at 100 psi will it’s 5 over at 50 psi?
— Doug

Expensive Doug,
I run into this consistently. I imagine {that a} pump gauge, since it’s really measuring the strain within the hose, a great distance from the valve, goes to be inherently inaccurate. I’ve plenty of completely different digital gauges, they usually all appear to learn inside 1psi of one another. That’s a lot ok for me. I like to recommend you imagine your digital gauge and never any of your pumps.

I don’t know if the discrepancy is linear or not, and I believe it relies on the gauge. Some gauges appear to have an preliminary offset, like if the spring contained in the gauge is bent, wherein case the discrepancy actually wouldn’t be linear.

I don’t know if there’s a commonplace to calibrate towards that’s simply obtainable. Don’t overthink it. Simply use your digital gauge.
― Lennard

Campagnolo cable housing.
A Klein Rascal about to be restored for driving.

Expensive Lennard,
At age 67, I’m most likely about your age, however my ardour for bikes remains to be sturdy. I not too long ago acquired a 1992 Klein Rascal body/fork/mission-control headset and I’m within the technique of constructing it up. My query is that this:

I actually like older Campy-style cabling, the stainless coils variety. I’ve used it earlier than and would love your recommendation as to the standard of one of these cable housing. Though I’ve some classic XT thumb shifters, I’m planning to simply use the friction mode, a minimum of for now, so I gained’t want the rigidity of listed shifting cables and housing.
— Pete

Expensive Pete,
Wow, you’ve stored that little Rascal in good situation all of those years! In case you imply the unlined little piece of coil fabricated from stainless-steel spherical wire (versus flat wire) that Campagnolo used to provide for the final little stretch from the chainstay cable cease to the rear derailleur, I’d not advocate it for lengthy cable runs, as a result of it has no liner and can consequently create extra friction.

The flat coil within the photograph of your white bike seems to be like commonplace lined brake cable housing with a transparent cowl. That might be used with frictional shifters. And also you clearly do perceive that listed shifting is not going to work with coil housing as a result of the compression of the housing leads to extra cable pull per shift required than the listed lever pulls on every click on.
― Lennard

Expensive Lennard,
Why are prime tube lengths on gravel bikes the size that they’re?

Some gravel bikes are touted as having new revised geometry, in contrast with highway bike geometry. From what I can inform they’ve merely prolonged the highest tube by 1cm (dimension 56). Huge deal, one whopping cm! What occurs to dealing with when the highest tube will get longer, and the stem will get correspondingly shorter? Does a 1cm enhance in prime tube size make a tangible distinction?

Professional highway riders use lengthy stems. Would they be higher off in the event that they make prime tubes longer and stems shorter? Would Caleb Ewan’s rear wheel skitter around much less throughout sprints? Would riders catapult over their handlebars much less typically? Would there be riots within the streets proclaiming the hazards of disc brakes… I imply lengthy prime tubes?

Again to gravel bikes and longer prime tubes. I’ve quick legs. My gravel bike has a 130mm stem. Having performed loads of mountain bike racing up to now, I really feel manner too far over the entrance wheel when the highway will get tough or free. Specialised got here out with the brand new Diverge EVO. I’m going to get a dimension medium (60cm prime tube) and put a drop bar on it with a 90mm or 100mm stem. I’m considering this can end in a greater dealing with gravel bike? Any ideas?

In case you inform me that lengthy stems decelerate dealing with, then how do mountain bikes, which have to make a lot tighter turns, get away with such lengthy prime tubes?
— John

Expensive John,
A few of the identical rationale is at work with fashionable gravel bikes as with fashionable mountain bikes. On mountain bikes, as prime tubes have gotten longer and stems shorter, handlebars have grow to be longer. Rather a lot longer. Sure, on the mountain bikes of the Nineteen Eighties and early Nineteen Nineties with 560mm lengthy handlebars, the lengthy stem, generally so long as 150mm, slowed down the dealing with by requiring extra hand motion to rotate the steering tube by means of a given variety of levels. Quick ahead to at present, the place the handlebar is 800mm lengthy and the stem is maybe 40mm lengthy. That lengthy bar is having the same impact to the lengthy stems of yesteryear, once more requiring extra hand motion to rotate the steering tube by means of a given variety of levels.

The primary technology of gravel bikes tended to have the identical handlebar, in addition to the identical prime tube and stem size as highway bikes. Now, the handlebars are flared out and wider, and the stem has grow to be correspondingly shorter to extend the steering quickness misplaced with the rise in bar width. The highest tube size needed to enhance to pair with the shorter stem. And, in the same method to what has occurred with the march of time to mountain bikes, the longer prime tube has moved the entrance wheel additional ahead relative to the ft, fingers, and butt, one thing you’ll undoubtedly recognize.
― Lennard


Lennard Zinn, our longtime technical author, joined VeloNews in 1987. He’s additionally a {custom} body builder (www.zinncycles.com) and purveyor of non-custom big bikes (bikeclydesdale.com), a former U.S. nationwide staff rider, co-author of “The Haywire Heart,” and creator of many bicycle books together with “Zinn and the Art of Road Bike Maintenance,” “DVD, in addition to “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado School.

Comply with @lennardzinn on Twitter.

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