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Discussion Starter · #1 ·
Hi all,

I'm still trying to figure out the best configurations for my new frame and I need more input. Most Ti frame top tubes are 31.8mm/ 1.25" diameter. However, Moots does theirs at 38.1mm/ 1.5" diameter for added stiffness. However, I was wondering whether the additional weight is worth it. There is also a 34.9mm/1.375" size top tube that I can specify.

So should I just stick with 31.8mm/ 1.25", go for broke with 38.1mm/1.5" or compromise and go inbetween at 34.9mm/1.375".

I'm 6'1" and 187pounds and will be using this frame for training and racing. The frame is going to be a size 58cm.

I want the added stiffness but I don't want to pay the weight panalty. Will a larger diameter top tube add dramatically to the stiffness of the frame? Not sure what dimensions other Ti manufacturers have their top tubes. Litespeed owners and Merlin owners, care to help and measure yours?

Regards,
Sean
 

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Unless they are cheap-ass tubes, the larger dia. tubes will be thinner than the smaller tubes. For the same weight, the tubes SHOULD be stiffer.
A steel 1 1/4 top tube is very stiff. A Ti 1 1/4 tube won't be as stiff.
 

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Ask Moots???

Your request is kind of silly if you ask me. If you want a particular builder to build you a frame, let them do it. They should be able to provide better guidance than anyone on this site. If they can't they aren't worth a darn and yo should try some other builder.

Litespeed constantly makes changes to their designs so they can tout the new model as "new and improved" and charge even more for it. The latest gimick is oversize seat tubes with big fat ugly seat posts.

You're also obssessing about an ounce of weight that won't make you or break you.

I'd worry about too much stiffness. A frame that's too stiff will ride like crap. You won't ride fast if you're constantly recovering from a major joslting due to some rough pavement. The '98 Litespeed Ultimate that I owned was a perfect example of too much stiffness.
 

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Discussion Starter · #4 ·
Hi C-40

Good point about the stiffness of the frame. I never thought about that. Kinda lost the plot of why I was moving to Ti in the first place. I ride a Cadd 4 and it was beating me on longer rides. So I wanted something that would last me forever and I could race as well without much lost to flex.

Do you roughly remember what size top tube the litepseed was? So that I have a gauge of the benchmark limit.

Regards,
Sean
 

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it's NOT the top tube...

In the case of the Litespeed Ultimate, the offending tube was undoubtedly the bladed downtube, combined with short chainstays that produced the crappy ride. The front end of the bike was totally unforgiving.

That many years ago, the TT could not have been too oversize, probably only 1.25 inch.

The other thing to remember with Litespeeds is that many of the tubes are NOT round either.

Unless you're in bad need of unusual geometry due to odd body proportions, perhaps you should consider a STOCK frame that you can test ride. A short test ride won't reveal much about the frame though. It usually takes hundreds of miles to become fully acquainted with a new frame.
 

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Discussion Starter · #6 ·
Thanks

Thanks for the advice C-40. I am trying to get a manufacturer to produce a frame and it is as much of an experience as an experiment for me. I have always been intrigued about things like this.

So far I have yet to come to a decision regarding the top tube. First it was going to be oversized 38.2, then 34.9 and now I am swaying more towards he 31.8/ 1.25". This is because I've seen most manufacturers only using this sized top tube. It looks as if only Moots uses the larger top tube. Probably as their tubing are thinner walled thus negating the additional weight effects of a larger tube.

I've specified an oval down tube and larger chainstays so I guess I should be sorted in terms of stiffness. I also doubt that a larger diameter top tube would increase the power transfer from me to the bike.

Regards,
Sean
 
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