Frame size vs wheelbase

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Dunnroamin
Posts: 30
Joined: 6 Jun 2013, 1:21pm

Frame size vs wheelbase

Post by Dunnroamin »

I'm an elderly man, and I have an inside leg measurement of about 27", for which the frame size charts indicate the need for a frame size of around 17". My knees don't bend as well as they used either, so I have been looking at "step-through" (women's) bikes. It seems, however, that as the frame size decreases, so does the wheelbase (the distance, as I understand it, between the front wheel axle and the rear wheel axle). Unfortunately, the wheelbase, or frame length are measurements not usually shown in bike specifications. I think I may have mentioned this problem before in this forum, but with no satisfactory conclusion. Basically, what I am looking for is a bike that has the wheelbase of 21" frame, coupled with a frame height of 17" (so I can reach the ground). This would, hopefully, enable me to raise the seat and, together with maximum setback, get the necessary leg stretch. I don't know if there are any 17" bikes for men on the market, but if there are, would they be likely to have a longer wheelbase than a 17" ladies frame. Finally, does anyone know whether there are makes and models that answer my requirements, I would be so grateful for any suggestions. D :?
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Vantage
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Re: Frame size vs wheelbase

Post by Vantage »

I dare say that someone will come along and explain this better than I, but unless the bike has unusual head and or seat tube angles, a longer wheelbased bike will have you stretched out to an uncomfortable and unhealthy position on the bike.
The type of bike you choose will also be a deciding factor in wheelbase. A tourer will be a bit longer than a race/road bike due to increased heel clearance. Wheel size might be worth thinking about also as if you're after 700c rims, there aren't that many bikes with a small frame (16-17") with 700c clearances.
You don't say what your preferred price range is, but Dawes do a 16" Galaxy for as little as £599 for the base model and I'm sure other makers have small frames but most will use 26" rims.
Bill


“Ride as much or as little, or as long or as short as you feel. But ride.” ~ Eddy Merckx
It's a rich man whos children run to him when his pockets are empty.
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531colin
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Location: North Yorkshire

Re: Frame size vs wheelbase

Post by 531colin »

Dunnroamin wrote:I'm an elderly man, and I have an inside leg measurement of about 27", for which the frame size charts indicate the need for a frame size of around 17". My knees don't bend as well as they used either, so I have been looking at "step-through" (women's) bikes. It seems, however, that as the frame size decreases, so does the wheelbase (the distance, as I understand it, between the front wheel axle and the rear wheel axle). Unfortunately, the wheelbase, or frame length are measurements not usually shown in bike specifications. I think I may have mentioned this problem before in this forum, but with no satisfactory conclusion. Basically, what I am looking for is a bike that has the wheelbase of 21" frame, coupled with a frame height of 17" (so I can reach the ground). This would, hopefully, enable me to raise the seat and, together with maximum setback, get the necessary leg stretch. I don't know if there are any 17" bikes for men on the market, but if there are, would they be likely to have a longer wheelbase than a 17" ladies frame. Finally, does anyone know whether there are makes and models that answer my requirements, I would be so grateful for any suggestions. D :?


You don't say why you think the wheelbase is important to you.....?
Chainstay length and front centre (BB axle to front spindle) are often listed.
Valbrona
Posts: 2687
Joined: 7 Feb 2011, 4:49pm

Re: Frame size vs wheelbase

Post by Valbrona »

Bikes with 26" wheels, as opposed to the more regular 700c wheel size, are perhaps a better choice for smaller riders. They can result in a better proportioned frame with more wheel clearance.

In your analysis 'Do I go for a frame that fits me lengthways or heightways' you should always base your decision on lengthways considerations, so consideration of wheelbase should be more important. Your average seatpost can go up or down a couple of feet these days ... there is plenty of height adjustment in bikes, but not so much lengthways adjustment.

If it is a utility bike with a step through frame you are after, well there are some out there. And the better ones tend to have internal gears and sometimes also drum brakes.
I should coco.
andyh2
Posts: 403
Joined: 24 Oct 2007, 8:49pm

Re: Frame size vs wheelbase

Post by andyh2 »

It does seem as if bike design follows (has to?) what the market says is right and if the market 'decides' a particular wheel size is necessary then frame compromises follow.

I'm not quite sure why, for example, a surly long haul trucker tourer in 42cm size has 75 degree seat angle and in 62cm size has 72 degree seat angle and differences, though not as great, in head tube angles across sizes. I'd have thought that if a particular frame geometry was good for a particular purpose then it would make sense to design all the frame sizes around that and then see what size wheels would sensibly fit each frame. The use of 26" wheels on some smaller frames goes someway towards that, but not as far as it could with the range of wheel sizes available. Or am I missing something and shorter and taller people need different frame geometries for the same purpose?

It would help to have more detail on what you're trying to achieve. I wonder if you're trying to achieve a low seat height so it's easy to reach the ground and maintain stability when setting off and stopping in particular. My Mum toured all over on her Galaxy (diamond framed 'mens' version), but over time struggled with starting and stopping especially with a load and mounting / dismounting. Her solution has been a Rans Fusion ST semi recumbent.
http://www.rans.com/bicycles/fusion-st.html

This design allows provides easy mounting with the step through frame and she can remain seated with both
feet flat on the ground, which she finds very helpful for starting / stopping especially when loaded. As always there are compromises and this design does not allow out of the saddle pedalling, but she's never done that anyway.

A less extreme (and costly) version of this could be achieved by choosing a frame with relatively relaxed angles and using a seat post with extra layback. A low bottom bracket height is also helpful.
Maybe something like the Paper Bicycle might be worth checking out;
http://www.paper-bicycle.com/hustle/
Brian73
Posts: 472
Joined: 11 Aug 2010, 10:32pm

Re: Frame size vs wheelbase

Post by Brian73 »

Decathlon have this in 2 sizes 26" and 700c

http://www.decathlon.co.uk/elops-100-ci ... nformation

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531colin
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Re: Frame size vs wheelbase

Post by 531colin »

Valbrona wrote:...............
In your analysis 'Do I go for a frame that fits me lengthways or heightways' you should always base your decision on lengthways considerations, so consideration of wheelbase should be more important. ...............


Bike fit "lengthways" is the distance between saddle and hand-grips. (and the horizontal distance between saddle and bottom bracket)
This has a lot to do with handlebar shape, stem length, seatpost setback, frame angles and fork offset. Wheelbase can be a completely separate variable.
Valbrona
Posts: 2687
Joined: 7 Feb 2011, 4:49pm

Re: Frame size vs wheelbase

Post by Valbrona »

531colin wrote:
Valbrona wrote:...............
In your analysis 'Do I go for a frame that fits me lengthways or heightways' you should always base your decision on lengthways considerations, so consideration of wheelbase should be more important. ...............


Bike fit "lengthways" is the distance between saddle and hand-grips. (and the horizontal distance between saddle and bottom bracket)
This has a lot to do with handlebar shape, stem length, seatpost setback, frame angles and fork offset. Wheelbase can be a completely separate variable.


Yes, understood. It is just that I was too polite to point out to the OP that wheelbase is a bit of a red herring; better to be looking at the bit in the geometry chart labelled 'Effective Horizontal Top Tube'.
I should coco.
sreten
Posts: 347
Joined: 29 Sep 2013, 10:59pm

Re: Frame size vs wheelbase

Post by sreten »

Dunnroamin wrote:I'm an elderly man, and I have an inside leg measurement of about 27", for which the frame size charts indicate the need for a frame size of around 17". My knees don't bend as well as they used either, so I have been looking at "step-through" (women's) bikes. It seems, however, that as the frame size decreases, so does the wheelbase (the distance, as I understand it, between the front wheel axle and the rear wheel axle). Unfortunately, the wheelbase, or frame length are measurements not usually shown in bike specifications. I think I may have mentioned this problem before in this forum, but with no satisfactory conclusion. Basically, what I am looking for is a bike that has the wheelbase of 21" frame, coupled with a frame height of 17" (so I can reach the ground). This would, hopefully, enable me to raise the seat and, together with maximum setback, get the necessary leg stretch. I don't know if there are any 17" bikes for men on the market, but if there are, would they be likely to have a longer wheelbase than a 17" ladies frame. Finally, does anyone know whether there are makes and models that answer my requirements, I would be so grateful for any suggestions. D :?


Hi,

What your saying doesn't make a lot of sense.

Image

rgds, sreten.
Dunnroamin
Posts: 30
Joined: 6 Jun 2013, 1:21pm

Re: Frame size vs wheelbase

Post by Dunnroamin »

531colin wrote:
Dunnroamin wrote:I'm an elderly man, and I have an inside leg measurement of about 27", for which the frame size charts indicate the need for a frame size of around 17". My knees don't bend as well as they used either, so I have been looking at "step-through" (women's) bikes. It seems, however, that as the frame size decreases, so does the wheelbase (the distance, as I understand it, between the front wheel axle and the rear wheel axle). Unfortunately, the wheelbase, or frame length are measurements not usually shown in bike specifications. I think I may have mentioned this problem before in this forum, but with no satisfactory conclusion. Basically, what I am looking for is a bike that has the wheelbase of 21" frame, coupled with a frame height of 17" (so I can reach the ground). This would, hopefully, enable me to raise the seat and, together with maximum setback, get the necessary leg stretch. I don't know if there are any 17" bikes for men on the market, but if there are, would they be likely to have a longer wheelbase than a 17" ladies frame. Finally, does anyone know whether there are makes and models that answer my requirements, I would be so grateful for any suggestions. D :?


You don't say why you think the wheelbase is important to you.....?
Chainstay length and front centre (BB axle to front spindle) are often listed.


Wheelbase comes into my reckoning because, it seems, as the frame size reduces, so does the length of the bike, which usually means the handlebars are almost touching my rather corpulent stomach. If the length of a frame is, initially, too long, so that I am having to lean too far forward for comfort, this can probably be corrected by a hinged handlebar bracket.
Dunnroamin
Posts: 30
Joined: 6 Jun 2013, 1:21pm

Re: Frame size vs wheelbase

Post by Dunnroamin »

andyh2 wrote:It does seem as if bike design follows (has to?) what the market says is right and if the market 'decides' a particular wheel size is necessary then frame compromises follow.

I'm not quite sure why, for example, a surly long haul trucker tourer in 42cm size has 75 degree seat angle and in 62cm size has 72 degree seat angle and differences, though not as great, in head tube angles across sizes. I'd have thought that if a particular frame geometry was good for a particular purpose then it would make sense to design all the frame sizes around that and then see what size wheels would sensibly fit each frame. The use of 26" wheels on some smaller frames goes someway towards that, but not as far as it could with the range of wheel sizes available. Or am I missing something and shorter and taller people need different frame geometries for the same purpose?

It would help to have more detail on what you're trying to achieve. I wonder if you're trying to achieve a low seat height so it's easy to reach the ground and maintain stability when setting off and stopping in particular. My Mum toured all over on her Galaxy (diamond framed 'mens' version), but over time struggled with starting and stopping especially with a load and mounting / dismounting. Her solution has been a Rans Fusion ST semi recumbent.
http://www.rans.com/bicycles/fusion-st.html

That is exactly what I am trying to achieve, plus a bit more. So far, in my search for a more conventional bike than I'm riding a present, which is a Dutch feet or crank forward design, the problem I consistently have is, when I can just touch the ground with my toes, I cannot get my foot on the rearmost pedal when it is at about 9 0'clock. With the pedal at its highest (12 o'clock), I can't raise my feet high enough to comfortably keep my foot on the pedal (due to having short femurs). To compensate this I have to raise the seat height in order to gain greater leg stretch, but results in my not being able to reach the ground. The reason I'm looking for what I call a "conventional" bike is because my Dutch "Special Needs" bike is excessively heavy to lift onto my towbar bike stand, and quite heavy to pedal, especially when trying to get up to sufficient speed to stay upright. I have considered the Rans, but they only seem to be available in the USA and, I'm told, would be very expensive to import into this country ('though why no established UK cycle retailer has not established a dealership baffles me).

This design allows provides easy mounting with the step through frame and she can remain seated with both
feet flat on the ground, which she finds very helpful for starting / stopping especially when loaded. As always there are compromises and this design does not allow out of the saddle pedalling, but she's never done that anyway.

A less extreme (and costly) version of this could be achieved by choosing a frame with relatively relaxed angles and using a seat post with extra layback. A low bottom bracket height is also helpful.
Maybe something like the Paper Bicycle might be worth checking out;
http://www.paper-bicycle.com/hustle/
sreten
Posts: 347
Joined: 29 Sep 2013, 10:59pm

Re: Frame size vs wheelbase

Post by sreten »

Hi,

FWIW the last unloved version of the Raleigh Chopper, the MK3 might
be exactly the sort of thing you are looking for, they go fairly cheap.

rgds, sreten.
PH
Posts: 13099
Joined: 21 Jan 2007, 12:31am
Location: Derby
Contact:

Re: Frame size vs wheelbase

Post by PH »

Good article here by Dave Yates a well respected frame builder which explains why the two most common questions, wheelbase and weight, are the wrong ones.
http://www.daveyatescycles.co.uk/custom ... ons-38.php
Dunnroamin
Posts: 30
Joined: 6 Jun 2013, 1:21pm

Re: Frame size vs wheelbase

Post by Dunnroamin »

andyh2 wrote:It does seem as if bike design follows (has to?) what the market says is right and if the market 'decides' a particular wheel size is necessary then frame compromises follow.

I'm not quite sure why, for example, a surly long haul trucker tourer in 42cm size has 75 degree seat angle and in 62cm size has 72 degree seat angle and differences, though not as great, in head tube angles across sizes. I'd have thought that if a particular frame geometry was good for a particular purpose then it would make sense to design all the frame sizes around that and then see what size wheels would sensibly fit each frame. The use of 26" wheels on some smaller frames goes someway towards that, but not as far as it could with the range of wheel sizes available. Or am I missing something and shorter and taller people need different frame geometries for the same purpose?

It would help to have more detail on what you're trying to achieve. I wonder if you're trying to achieve a low seat height so it's easy to reach the ground and maintain stability when setting off and stopping in particular. My Mum toured all over on her Galaxy (diamond framed 'mens' version), but over time struggled with starting and stopping especially with a load and mounting / dismounting. Her solution has been a Rans Fusion ST semi recumbent.
http://www.rans.com/bicycles/fusion-st.html

This design allows provides easy mounting with the step through frame and she can remain seated with both
feet flat on the ground, which she finds very helpful for starting / stopping especially when loaded. As always there are compromises and this design does not allow out of the saddle pedalling, but she's never done that anyway.

A less extreme (and costly) version of this could be achieved by choosing a frame with relatively relaxed angles and using a seat post with extra layback. A low bottom bracket height is also helpful.
Maybe something like the Paper Bicycle might be worth checking out;
http://www.paper-bicycle.com/hustle/


Your suggestions (bold) are the directions I have already been trying to follow, unfortunately few, if any specifications include the angle of the rear tube or the height of the bottom bracket, and staff are usually non the wiser either. Also, to be able to give the bike more than just a cursory, instore sit upon, one has to practically agree to buy the bike (especially if it has to be specially ordered in) before the bike can be tried out at home. I do understand the retailer's reluctance on this point, but it does make it harder to adequately test ride before deciding.
Dunnroamin
Posts: 30
Joined: 6 Jun 2013, 1:21pm

Re: Frame size vs wheelbase

Post by Dunnroamin »

andyh2 wrote:It does seem as if bike design follows (has to?) what the market says is right and if the market 'decides' a particular wheel size is necessary then frame compromises follow.

I'm not quite sure why, for example, a surly long haul trucker tourer in 42cm size has 75 degree seat angle and in 62cm size has 72 degree seat angle and differences, though not as great, in head tube angles across sizes. I'd have thought that if a particular frame geometry was good for a particular purpose then it would make sense to design all the frame sizes around that and then see what size wheels would sensibly fit each frame. The use of 26" wheels on some smaller frames goes someway towards that, but not as far as it could with the range of wheel sizes available. Or am I missing something and shorter and taller people need different frame geometries for the same purpose?

It would help to have more detail on what you're trying to achieve. I wonder if you're trying to achieve a low seat height so it's easy to reach the ground and maintain stability when setting off and stopping in particular. My Mum toured all over on her Galaxy (diamond framed 'mens' version), but over time struggled with starting and stopping especially with a load and mounting / dismounting. Her solution has been a Rans Fusion ST semi recumbent.
http://www.rans.com/bicycles/fusion-st.html

This design allows provides easy mounting with the step through frame and she can remain seated with both
feet flat on the ground, which she finds very helpful for starting / stopping especially when loaded. As always there are compromises and this design does not allow out of the saddle pedalling, but she's never done that anyway.

A less extreme (and costly) version of this could be achieved by choosing a frame with relatively relaxed angles and using a seat post with extra layback. A low bottom bracket height is also helpful.
Maybe something like the Paper Bicycle might be worth checking out;
http://www.paper-bicycle.com/hustle/


Your suggestions (bold) are the directions I have already been trying to follow, unfortunately few, if any specifications include the angle of the rear tube or the height of the bottom bracket, and staff are usually non the wiser either. Also, to be able to give the bike more than just a cursory, instore sit upon, one has to practically agree to buy the bike (especially if it has to be specially ordered in) before the bike can be tried out at home. I do understand the retailer's reluctance on this point, but it does make it harder to adequately test ride before deciding.
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