replace top tube to improve ride

[Clark Fitzgerald]

Has anyone ever replaced a top tube on a steel bike to change the ride characteristics? Can you tell the difference on a bike with a flexible top tube? Could it make a difference on a bike with 2 inch wide tires?

I've been reading Jan Heine's book All Road Bike Revolution, and the section on frame stiffness got me thinking about why my commuter bike, an XL 90's Specialized Hard Rock, feels kind of dead. I measured the top tube- it's 1.25 inches in diameter, larger than other bikes that I've had. I recall listening to Tom Ritchey praise flexible top tubes.

I'm wondering if switching from a 1.25 inch to a 1 inch top tube will add some needed frame flex for me. I'm 165 lbs, and 99% of my riding on this bike is spinning in easy gears. I don't carry a rear load, and I don't use it for singletrack.

Could this be a mostly DIY project? I would never consider doing it myself on a nice bike, but this ain't a nice bike. Cutting out the old tube, grinding down the old TIG welds, and mitering the new tube all seem doable, with patience. I would need a skilled welder to do the actual welding or brazing though. If it works OK I'd get it powder coated.

[Clark Fitzgerald]

I asked my local frame builder about this idea, and here's what he had to say:

This is not something I would recommend doing.  Since the frame is TIG welded my concern would be the integrity of both the head tube and seat tube after the top tube was removed and the weld remnants filed away.  TIG welding concentrates a lot of heat at the weld area, which can affect the tubes integrity and so putting it through another heat cycle by brzing in another top tube is less than wise.  There are a lot of other options to "liven" up the feeling of a bike.  Wheels and more importantly tires play a huge role.

I'm going to take his advice and leave the frame alone.

--
You received this message because you are subscribed to a topic in the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/rbw-owners-bunch/F2Xb1h39K4w/unsubscribe.
To unsubscribe from this group and all its topics, send an email to rbw-owners-bun...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/c77684e6-f964-429a-bd40-6c09bd7eb440n%40googlegroups.com.

[John Hawrylak]

Dont know anyone who did it, but some considerations:

If the frame is Tig welded, you may have hard time with a 1" TT, just from a fabrication aspect. 

Also, Tig welding in the 90's generally used tubing with a larger wall thickness for margin of safety.

If a lugged frame, then the cost should be the same as replacing a broken TT with repainting the frame.

If the TT was oversized (OS) tubing, the DT is likely to be be OS (1-1/4" vs 1-1/8").    Again, the DT maybe a thicker tube also.

Jan Heine's Mule tubeset uses a 7-5-7 OS DT with a 7-4-7 1" TT with reportedly decent flex (the 7-5-7 DT would be similar to a 9-7-9 1-1/8" DT).   Would suspect your DT is thicker than 0.5mm, but perhaps keeping the ratios of TT to DT the same would produce similar results or at least get you in the ballpark.  

The TT wall thickness is also a consideration.   A 1-1/8" tube is about 30% stiffer than a 1" tube of the same wall thickness (due to difference in OD).   So 1" TT should add flex to the frame, if the same wall thickness is used.  T A thinner 1" TT would add more flex.

John Hawrylak

Woodstown NJ

[John Hawrylak]

Jan Heine sells 26"x 1.8" supple tires by Panaracer.  perhaps a $72 investment would 'soften up' your ride to the maximum extent possible. If still too harsh, a new flexible frame would be the next step.

I agree with the Tig welding affecting the head and seat tube integrity if welded a 2nd time (the welds 'heat affected zone').  Your builder was knowledgeable to point this out.

John Hawrylak

Woodstown NJ

[Kainalu V. -Brooklyn NY]

As your framebuilder said, probably best left alone. But, as an amateur brazer, I'd solve the "problem" by cutting the tubes a bit less, leaving nubs to use as lugs for a tube with a outside diameter that matches the inside diameter of the existing toptube. This wouldn't get you down to 1', but it would be relatively easy and avoids welding the headtube with TIG level heat, just a little low temp silver filler. I'd love to hear why this might be a bad idea from those more knowledgeable.

-Kai 

On Sunday, March 21, 2021 at 11:33:29 AM UTC-4 Clark Fitzgerald wrote:

[Christopher Cote]

This reminds me of a, possibly apocryphal, story about a major motorcycle manufacturer that was testing a new motocross bike. The test rider complained that it didn't turn in well, and one of the engineers grabbed a cordless drill and drilled a hole in the frame behind the headtube. After a few more laps, the test rider proclaimed the handling issues fixed.

I don't advocate drilling holes in your frame, but like John said, good tires will make a huge difference in how the bike rides.

Chris

On Sunday, March 21, 2021 at 11:33:29 AM UTC-4 Clark Fitzgerald wrote:

[Clark Fitzgerald]

Kai- A "TIG lug"- cool idea. The poor man's bilaminate frame :)

To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/afc64e43-1631-452c-a12e-8282a1c277b2n%40googlegroups.com.

[Patrick Moore]

I can vouch for the suppleness and fast-rolling quality of the 1.8" RH Naches Pass tire, in the "normal" as well as the "EL" versions. In my experience, they give up little, perhaps nothing, to the sublime rolling quality of the ultra light, 175-gram RH Elk Pass.

But I doubt whether even the best tire will make a dead bike feel alive. I used the Elk Pass on my erstwhile 2003 Curt Goodrich Riv custom, then used the same wheels and tires on the replacement Matthews frame. The Curt just felt sluggish* in a way that the Matthews does not, and I was immediately struck, on first riding it, how "easier to pedal" the latter is when, say, coming to an incline or turning into a headwind -- all this especially noticeable because on a fixed gear one cannot gear down.

*Relatively speaking, that is, compared to, say, the 1999 Joe Starck custom (also shod with the Elk Pass) and to other frames built of less robust tubing. The 2003 wasn't horrible, just noticeably "non-optimum."

[Clark Fitzgerald]

I realized that there's another reason for the ride feeling like it does. Usually I ride this as a commuter, with a Kryptonite New York lock strapped on top of the rear rack, so much of my impression of the ride comes from this. Removing this saved about 7 lbs from right on top of the rear wheel. The ride is noticeably different without this weight, because the bike is much easier to rock from side to side. Once my current tires wear out maybe I'll try something high end and see what else that does for it.

Perhaps frame tubing stiffness makes only a small difference in ride feeling, while cargo weight distribution and tires make big differences.

--
You received this message because you are subscribed to a topic in the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/rbw-owners-bunch/F2Xb1h39K4w/unsubscribe.
To unsubscribe from this group and all its topics, send an email to rbw-owners-bun...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/CALuTfguAc_0caSpNpAnLJ1Fomjb_sQ1Nh_%2BkdbgMciH%2B6wzjog%40mail.gmail.com.