Short chain stays & handling
 

I bought a used 58 CM Tommassini road frame with a 100 CM wheel base and 40.5 CM chain stays. There is no chain stay bridge. Based on some research it looks like the standard chain stay length is 42 CM. Are these short chain stays a problem? Will it be too hard to control?

There is no "standard" chainstay length but yours is typical for a sports bike and the handling should be fine. Chainstays in the 42 cm range are more typical of Touring bikes and are chosen mostly to create heel clearance when the bike has panniers mounted.

Handling is mostly controlled by headtube angle, fork rake and the resulting "trail" value they produce. Chainstay length and wheel base are minor contributors.

Thats fine. A touring bike has longer which is good for carrying weight and slow, causal riding. Short stays are more useful for sprints and quick climbs. Handing is more affected by the head tube angle and fork.

As others have said, your bike is typical for a spot bike and offers more nimble steering, but it can come at a cost. As frames get larger, and the seat post is extended, the seat tube angle causes the saddle to be father back. This changes the weight distribution pushing the center of gravity back while the short chainstays pushed the rear axle forward.

Obviously you'll never be so far back that you're behind the axle, but if you're riding a 58cm frame with a decent amount of post showing, you may discover a few handling quirks, especially if combined with a short stem. There'll be less weight on the front wheel and this may (that's may, not will) make the bike more prone to front end shimmy on long, fast descents. On steep climbs your already back CofG will shift farther back, and many find this causes problems keeping the front wheel down when starting or accelerating. You'll need to compensate by shifting weight forward to manage this.

There's also the issue of chain angle. The shorter stay increases the chain angle for any non-aligned gear combination. IMO not enough to make a marked difference in performance, but you'll find that you need to trim the FD more often as you shift in the rear. (Di2 does this for you, but the benefit probably isn't worth the price). However if you're riding with a non-trimable index FD, it may reduce your options by one gear or so.

None of this is necessarily a problem, but things to be aware of and manage.

On the bright side, if you like to show off, short stay tall bikes are easier to do wheelies on.

Handling is very subjective. I've ridden over 200k-miles in the past 30-years on everything from custom-built track-bikes with 90cm wheelbase & 37.5cm chainstays, TT & crit-bikes of all sorts, MTBs, to touring-bikes with 105cm/42cm specs. Sure they handled differently, but I wouldn't say one was hard or more difficult to control relative to the others.

The idea is you visualize a line on the road you want the bike to follow, then you give it the steering-inputs needed to make it follow that line. Then take feedback on whether it's on that line or not and correct your inputs. Repeat, repeat, repeat, etc. On all the bikes I've ridden, I can always make it follow the line I want, but some may require different levels of steering-force and turning-angle.

There are different arenas of handling, are you talking about parking-lot maneuvers with loaded panniers? Bombing down a twisty mountain road @ 60mph with switchbacks? Slicing through the inside of the pack in a crit? Without knowing exactly the conditions you ride in and what kind of handling you want, it's hard to say how that bike will work for you. Track, crit and road-race bikes are optimized for 25-50mph speeds. Faster than that and they get a little nervous feeling and I'd much prefer a touring bike. Slower than that, like if I was racing an autocross course on my back patio, I would design a bike with 70cm wheelbase and 30cm chainstays.

It really comes down to the speeds and type of riding you want to do. There's no one-size-fits-all solution that can be best at everything.

Only if you have the "wheelie gene"... Unfortunately, in the genetic lottery, I won the "embarrassing crash gene" instead! :(

A few points- I wouldn't call a 42cm stay touring at all. Maybe club/sports touring but not at all the length for large panniers and heel clearances or fore/aft weight distribution. But on this list I wouldn't expect most to really undersatnd this.

I always looked at the stay length as a device to balance the fore/aft weight. As has been alluded to before.

The stay length expection suffers from the "bigger is better" problem. Except it's "smaller is better" by marketing. I try to make my stays as long as I can. Chain line, tire/fender clearances, high speed stability all work better if I avoid the "smaller is faster" media BS. Andy.

Thanks to all for your thoughtful analysis. I live in NE FLA so there is no concern about climbing since it is flat. I'm going ahead with a build up into a road bike. Thanks again.

Yeah, your right that 42 cm isn't a "real" touring bike length as they tend to be 45-46 cm but it's longer than most racing/sports bikes which run around 40 cm. CX bikes are typically around 42 cm.

It's not faster, it's nimbler. And it corrects the weight distribution if you run a stem with any length much below your seat.

I think many consumers don't get this distinction. I also think marketing goes to the bank every day based on this lack of understanding. I had hoped my use of quotes would suggest that i was using this phrase (smaller is faster) in the marketing sense. I could have used the work "quicker" and meant the same.

As i said in my post, I use the stay length as the way to balance the weight. Was I not clear enough? Andy.

Tommasini Project
 

I initially posited my questions here because a bike store owner (Gainesville, FLA) had questioned the stability of the Tommasini frame. He told me he thought I would have handling issues. He was concerned about the "short chain stays." He tried to sell me other stuff. Based on the wisdom I gleaned here I ignored him and built the frame up with parts off of a 70's road bike and some new stuff. And boy am I glad I did (pics attached.) The Tommy project bike is nimble and fun as heck to ride. It weighs in about 24.8 lbs and is stiff and responsive. I used the following from old stock: Sugino Mighty Aero crank, Shimano 600 rear derailleur, Dura ace shifters, and Shimano 600 hubs with Super Champion rims. New equipment includes Gatorskin Ultras (25mm), Campy Veloce brakes, Nitto 220mm stem, Tektro Brake Levers and handlebars.

I want thank all of you who weighed in here and helped me move forward. The build was fun with lots of little problem solving along the way. I managed to fit the old wheels to the 130mm dropout opening. The rusted dropout adjustment screws did not survive (I may need a machine shop to drill one out.) I'm not sure about the vintage of this frame (if you have any ideas about a Tommasini Prestige with the Air fork, please let me know.) The fairly upright posture works for my nearly 60 year old body.

I'll need to add a front derailleur altho here in sunny and flat NE FLA I use about 3 gears depending on wind conditions. Thanks!

Super high, super stubby stem is gonna affect handling more than stubby chainstays. I can't imagine really enjoying all those traits on one bike.