Road Bike Info & Discussion -*ASK ROAD QUESTIONS HERE*-

PB Forum :: Road Cycling and Touring
Road Bike Info & Discussion -*ASK ROAD QUESTIONS HERE*-
Author Message
Posted: Apr 6, 2020 at 16:23 Quote
newbermuda wrote:
Im a newb on road stuff and i need some sizing advice. 6'2 tall, have a 6'6 wingspan, and currently riding a 56cm steel frame road bike (bought from a friend who ensured me that "56cm fits anyone above 6ft" Blank Stare )

Now that i've done a few bigger rides on it, I find that its fine on gravel/singletrack but it feels sketch on road over 30mph, so I wanna buy something else. is a 61cm too big for someone my size? i'm looking at a specialized CruX expert in that sizing. I also notice that it comes with a 110mm stem. is it a bad idea to upsize on frame and run a shorter stem (like 70-80mm)?
Short stems on road bikes are terrifying. You're likely wanting to land on a 58. What length stem and width bars do you have?

Posted: Apr 6, 2020 at 16:45 Quote
newbermuda wrote:
Im a newb on road stuff and i need some sizing advice. 6'2 tall, have a 6'6 wingspan, and currently riding a 56cm steel frame road bike (bought from a friend who ensured me that "56cm fits anyone above 6ft" Blank Stare )

Now that i've done a few bigger rides on it, I find that its fine on gravel/singletrack but it feels sketch on road over 30mph, so I wanna buy something else. is a 61cm too big for someone my size? i'm looking at a specialized CruX expert in that sizing. I also notice that it comes with a 110mm stem. is it a bad idea to upsize on frame and run a shorter stem (like 70-80mm)?
Off hand, I'd say you're more suited to a 58cm frame with a full length stem... If you're going under 100mm or over 130mm you're compensating for a mis-sized frame. Shorter stems will make a road bike feel less stable also, more twitchy... so you'll be putting yourself right back in the situation you're trying to escape now.

Posted: Apr 6, 2020 at 17:51 Quote
Interesting, thats the opposite effect as i would've expected (since shorter mtb stems usually = more stable). I'll start looking for a 58cm then.
current cockpit is 100mm stem and 42cm bars

Posted: Apr 6, 2020 at 18:03 Quote
newbermuda wrote:
Interesting, thats the opposite effect as i would've expected (since shorter mtb stems usually = more stable). I'll start looking for a 58cm then.
current cockpit is 100mm stem and 42cm bars
The added stability in MTB comes from the longer wheel base and tt length, the shorter stem exists to keep your posture correct and to sightly increase steering speed.

Generally wider bars and longer wheelbase will increase stability.

Posted: Apr 6, 2020 at 18:49 Quote
i'm 5'7 and I ride a 54cm frame, so 56cm for you must be way small. I'd look for the sizing chart on the CruX and go by that. I think the roadies have bike sizing pretty dialed in. I doubt a short stem on a road bike is a good idea. My first road bike was a Crux. It's a good choice.

Posted: Apr 6, 2020 at 19:40 Quote
newbermuda wrote:
Interesting, thats the opposite effect as i would've expected (since shorter mtb stems usually = more stable). I'll start looking for a 58cm then.
current cockpit is 100mm stem and 42cm bars
It's a radius arm... the longer the stem then the longer the radius and the further you have to move the bar to move the wheel a given amount. Shorter stern, shorter radius and each motion translates to more motion at the axis.

Posted: Apr 7, 2020 at 15:55 Quote
I went from a 56 Allez to a 58 Diverge when I got my 2nd road bike, there was a very noticeable increase in stability between the two (probably slightly due to a difference in geometry too). I'm 6ft, with a 110m stem it felt pretty spot on.

Posted: Apr 7, 2020 at 16:07 Quote
I 'm 6' and I'm on a 56 with 110mm stem.

Posted: Apr 7, 2020 at 16:13 Quote
badbadleroybrown wrote:
I 'm 6' and I'm on a 56 with 110mm stem.
Likewise.

Posted: Apr 7, 2020 at 16:16 Quote
I’m 6’4” with long legs, and I ride a 58. My ideal size would probably have a 57-57.5 effective TT.

Despite my height, I can actually get comfortable on some 56 bikes. Anyways, I rode 58 for the stack, and the stability Dingus mentions.

I would definitely agree that a 60 and up is too big for a 6’2” rider, unless you have a huge torso, or intend to ride with moustache bars.

Posted: Apr 7, 2020 at 16:33 Quote
newbermuda wrote:
Interesting, thats the opposite effect as i would've expected (since shorter mtb stems usually = more stable).

It's not the short stem that makes it stable, it's the long bike that requires a short stem. For a given bike, a long stem will make it more stable until the point at which the rider is about to go over the front, which happens slightly sooner with the long stem.

Modern, long bikes that require short stems also tend to have slacker head-tube angles. It's difficult to feel the effects of each variables when everything is changing.

Posted: Apr 7, 2020 at 17:20 Quote
I'd agree with that on mountain but much less so on road bikes

Posted: Apr 7, 2020 at 23:18 Quote
badbadleroybrown wrote:
I'd agree with that on mountain but much less so on road bikes

Yah. I've found that on road bikes, long stems create stability by eliminating twitchiness and feedback when pedaling uphill.

Posted: Apr 7, 2020 at 23:49 Quote
VTwintips wrote:
Yah. I've found that on road bikes, long stems create stability by eliminating twitchiness and feedback when pedaling uphill.

It's true. It's also true on mountain bikes. You can test it by using a very short stem and a very long stem on the same bike over moderate terrain. Don't use two different bikes, though, as an old-school bike with long stem is likely to be less stable for a variety of reasons.

Road bikes not only have a long stem, but the added length of the bar's reach and the extension of the hoods. That's a lot of effective "stem" length! This doesn't help with chassis stability, which can be felt when riding with your hands off the bar, but it does slow the steering response and increase the recentering force when your hands are on the bar.

Posted: Apr 8, 2020 at 5:49 Quote
Incorrect RMR... I've experimented plenty with same bike different stems and stems as an isolated variable make an enormous difference. I've ridden 54cm - 58cm bikes with stems from 90mm - 140mm. Road bikes lack the dynamic positioning of mountain bikes and have a more rear weighted geometry bias universally; and with that, longer stems don't pull you over the front, they bring you lower and extend your arms while slowing responsiveness. Head angle plays a role but the range of angels on road bikes is narrow with much less categorical distinction driving geometry.


 
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