Jul 20, 2001 11:19 PM
|with my present road bike i have about 3/4 inch standover clearance. being fitted for a new bike the suggestion is that i have 1 1/2 to 2. as i feel comfortable with the 3/4 and the way my present bike feels..what reasons are there for going to a smaller frame? it would be going from a 51 to a 48 or 49.|
|re: standover height??????||carbonguy|
Jul 20, 2001 11:27 PM
|your should be more worried about top tube length stand over is not as big of a concern. yes you do NEED standover clearence. just make sure you top tube isn't to long or too short...Just my 2 cents|
|re: standover height??????||PsyDoc|
Jul 21, 2001 5:12 AM
|As carbonguy already stated, you should be more concerned about your toptube length. Seeing as how you like the fit of your current bike, I will assume that the toptube length is about right. But, standover height should not be ignored from a safety standpoint. Is the 3/4" standover clearance with your shoes on or off? If the standover clearance is with your shoes off, then you should be alright. If not, then you may want to ride wearing a cup...just kidding. Seriously, with only 1.9cm (3/4") of standover clearance, you could be faced with a situation one day where you have to come off your seat quickly and there is a good chance you could do some serious damage to "the boys" or worse. However, that day may never come. But, if your current standover clearance feels fine and you like it that way, then I do not see any reason to increase it. There are folks who ride with a negative standover clearance.|
|re: standover height??????||SteveS|
Jul 21, 2001 6:00 AM
|I think 1.5-2.0" on a roadbike is excessive, part of the thinking of riding a too small frame. It presents the usual problem of handlebar placement due to a shorter headtube unless you like a maximum difference between you saddle and handlebar height. One inch should be sufficient.|
|get a new shop!||JohnG|
Jul 21, 2001 9:17 AM
|Anyone suggesting 2" of standover doesn't know what the H#ll they're talking about! Either that or they have a "perfect" frame they are trying to dump on you. :) Unless you are a serious racer this type of standover is WAY inappropriate. It goofs up the saddle-bar drop and will complicate reach issues.
Use the geometry from your current ride to estimate what you want in your new frame. Take a detailed set of measurements (including set-back) on the seat tube and you should have a good baseline to make an intelegent choice.
good rides JohnG
|2-4cm is adequate....||C-40|
Jul 21, 2001 2:28 PM
|Your shop didn't mention that going to a smaller frame not only increases standover clearance, but also increases saddle to bar distance, which can be a problem.
I always measure standover clearance in bare feet, and try to get 3-4cm. More clearance is unnecessary.
Top tube length is important, but so is seat tube angle. Some of the others posters have failed to mention "effective top tube length". Effective top tube length takes into consideration both the seat tube angle and top tube length when comparing different sizes or brands of frames. Basically, every degree of steeper seat tube angle lengthens the "effective" top tube by about 1cm (in your frame size). If you fail to consider differences in seat tube angle, you may make a faulty comparison.
Jul 21, 2001 8:47 PM
|every degree of steeper seat tube angle lengthens the "effective" top tube by about 1cm (in your frame size). |
In the above statement, what do you mean by "steeper"? Steeper than what? Example? I haven't found any mention of this on the web sites that describe ideal theoretical frame fit...
|steeper than? C-40||carbonguy|
Jul 22, 2001 9:48 AM
|C-40 did you meen "slacker" seat tube angle lengthens the "effective" top tube by about 1cm (in your frame size). ???????????|
|74 is "steeper" than 73...||C-40|
Jul 22, 2001 10:16 AM
|Your thinking is backwards. If you have a 74 degree seat tube angle on a frame, the saddle must be moved back further (than one with a 73) to place the knee in the same position relative to the bottom bracket. This effectively lengthens the top tube.
For example, a 55cm Colnago with 74 degree seat tube angle and 54.3cm top tube will fit the same as a 55cm Litespeed with a 73 degree seat tube angle and a 55.5cm top tube length.
|74 is "steeper" than 73...||carbonguy|
Jul 22, 2001 4:42 PM
|in one of your post you said "steeper seat tube angle lengthens the effective top tube by about 1cm (in your frame size). If you fail to consider differences in seat tube angle, you may make a faulty comparison". then you said "For example, a 55cm Colnago with 74 degree seat tube angle and 54.3cm top tube will fit the same as a 55cm Litespeed with a 73 degree seat tube angle and a 55.5cm top tube length". the 74 degree seat tube is steeper then the 73 degree right? so the same size bike with a 73 degree seat tube has a longer top tube... right? and the 73 degree is "slacker" then the "steeper" 74 degree seat tube. I might be totally mistaken and I have seen you post alot on this site and you do know what your talking but I think one of us is confused.|
|Yes, you are confused.||Kerry Irons|
Jul 22, 2001 5:19 PM
|Picture this: you have a frame with a 73 seat tube angle, you increase the angle to 74 degrees and the top tube is "pushed forward" about 1 cm. Since you want to keep the saddle position the same (relative to the BB), you have to move the saddle back 1 cm to compensate. For the same stem length, the handlebars will be about 1 cm farther away from the saddle. THEREFORE, the steeper frame has a longer "effective top tube length" than the frame with the 73 degree seat tube.|
|Yes, I am confused.||carbonguy|
Jul 22, 2001 5:35 PM
|yea that makes sense and you can see where it gets confusing.|| |