# Has anybody ever experimented with different size wheels



## Psycolist (7 Dec 2013)

For reasons of economy I am toying with the idea of having a 26" wheel at the front and a 700c wheel at the back on an off road build for the new year. Anyone out there ever tried it or have any thoughts on the idea ?


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## GrumpyGregry (7 Dec 2013)

What size wheels is the frame designed for?


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## zizou (7 Dec 2013)

Some manufacturers have sold bikes with different sized wheels (specialized big hit downhill bike had a 24" rear and 26" front and there were a few 69er trail bikes with 26" rear and 29" front).

Its always been the bigger wheel on the front rather than the rear though.


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## Psycolist (7 Dec 2013)

Its a matter of popping a pair of forks suitable for 26" wheels at the front of a frame that is built for 700c wheels. As I say, its a matter of economy, I have a semi decent pair of 26" forks, but my frame takes a 700c wheel. I have used it this year as a 29er, with poo forks at the front. Rather than retain the the poor quality forks, I wondered if I could utilize the better quality 26" wheel forks on the same frame that uses the 700c wheel at the back ?


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## BimblingBee (7 Dec 2013)

The geometry of the frame will likely be all wrong which may make it weaker. Assuming you will be using this to mountain bike on then down hills may well be errr.... interesting (as well as up, across and on the flat!)


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## Psycolist (7 Dec 2013)

That was a major reason for asking for other peoples experience or thoughts. Of course the geometry is going to be "different", but is it going to compromise strength ?? Its not worth injuring myself, or risking injury anyway. I dont think that dropping the front end of the "shape" of the bike would cause any additional stress, thats what happens when the suspension compresses anyway. BUT I am not a structural engineer and wanted other peoples input to perhaps put things into perspective. I should have been clearer in the origonal post I spose :>(


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## ufkacbln (8 Dec 2013)

The problem may be the steering and stability.

If a frame is designed for two different size wheels then it will work.

If however you use a smaller wheel at the front it alters the whole geometry of the bike.

The angle of the headset is changed, and this will alter the forks.

The trail is calculated from a straight line drawn through the head angle and a vertical line through the hub.

If the head angle becomes steeper, than the trail will shorten making the bicycle more twitchy and less stable.


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## Psycolist (8 Dec 2013)

Cunobelin said:


> The problem may be the steering and stability.
> 
> If a frame is designed for two different size wheels then it will work.
> 
> ...


 Cool. Thats a very helpful bit of info, cheers.


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## mickle (8 Dec 2013)

The outside diameter of a 700 x 25c road bike tyre is not far off the diameter of a 26 x 2.125 mountain bike tyre. But that would look silly - I'm guessing you want to use tyres of similar sections if not diameter. 
Raising the front of a bike by an inch changes the head angle by about a degree so it might be possible to fit your smaller front wheel, without any detrimental effect on the handling, simply by fitting a slightly longer (suspension) fork. The distance between the contact point of the tyre and an invisible line described by the headtube steering centre is the thing you're trying to preserve. Measure the height of the axles and the difference will tell you how much longer your fork needs to be.


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## Psycolist (8 Dec 2013)

mickle said:


> The outside diameter of a 700 x 25c road bike tyre is not far off the diameter of a 26 x 2.125 mountain bike tyre. But that would look silly - I'm guessing you want to use tyres of similar sections if not diameter.
> Raising the front of a bike by an inch changes the head angle by about a degree so it might be possible to fit your smaller front wheel, without any detrimental effect on the handling, simply by fitting a slightly longer (suspension) fork. The distance between the contact point of the tyre and an invisible line described by the headtube steering centre is the thing you're trying to preserve. Measure the height of the axles and the difference will tell you how much longer your fork needs to be.


Intersting variation on the same lines as Cunoblin. Thats got my grey matter spinning for different solutions to maintain the geometry. Very useful thanx.


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## martint235 (8 Dec 2013)

I've been seeing a lot of adverts for a 27.5inch tyre, maybe that's the way to go.


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## lukesdad (9 Dec 2013)

mickle said:


> The outside diameter of a 700 x 25c road bike tyre is not far off the diameter of a 26 x 2.125 mountain bike tyre. But that would look silly - I'm guessing you want to use tyres of similar sections if not diameter.
> Raising the front of a bike by an inch changes the head angle by about a degree so it might be possible to fit your smaller front wheel, without any detrimental effect on the handling, simply by fitting a slightly longer (suspension) fork. The distance between the contact point of the tyre and an invisible line described by the headtube steering centre is the thing you're trying to preserve. Measure the height of the axles and the difference will tell you how much longer your fork needs to be.


 The whole reason for doing this I believe is economy, I don't think he's going to wanna erm, 'fork' out on another fork !


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## Psycolist (9 Dec 2013)

forkryingoutloud


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## Psycolist (13 Dec 2013)

Well, thanx to all that chipped in. Being an awful, wet foggy day, I went ahead and tried the 26" fork idea on my existing 29er. I took the relevant measurments suggested both before and after the change as best I could. Interestingly, none of them changed by more than 10mm and the angle of the head set / forks / front wheel was not measurably different. I think this may have been because the "better" forks, having more travel, were longer then the forks I removed, compensating for the smaller wheel. By 3pm, it had at least stopped raining, so I took it out for a very short spin along a local track that I use for "testing" new ideas. The ride involves about 3/4mile on roads, then 1-1/2miles off road on a mixture of hardpack, grass, a little gravel section and since a bulldozer has been employed to get rid of a section of hedge, deep mud ! The bike felt no different on the road section, other than feeling much more "action" at the front end, but none of the twitchiness that was suggested may be felt. Once hitting the hardpack, I found it to be very slick on the surface, but was soon confident in the bike to up the anti and start pushing things. I went back to the start of the hardpack and firmed up the spring action, and then did the same again. Starting from the begining, I was pushing from the first turn of the pedals. It felt great, tracking the ground without any handling issues, onto the grass, then the gravel then the mud. The bike was markedly better with these replacement forks, without any of the possible problems showing up. Of course there is alot more testing to do, but by this time, I looked like the abonomable mud man, and the wife was due home, so a quick hose down for me and the bike, and a cuppa waiting for her ladyship when she got home. But all in all, I'm well pleased with todays efforts.


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## Psycolist (30 Dec 2013)

Just to finish my contribution to this thread, I have now completed over 100 miles on the new set up of 29er rear and 26er front. The most noticable change in my bike is that the quality of the fork, allowing me to feel much more confident in pushing the boundries when 'off road'. The quality improvement of the forks action, all be it still a sub £100 set of SR Suntour XCR, coil spring and pnuematic lock facility, over the origonal fork is well worth the effort involved in the change over. I'm not totally convinced that it hasnt caused ANY downside. At speeds over 25mph while on road, there does seem to be a certain twitchy feeling to the steering that I had never noticed before. However, that is the only thing I have noticed that could be deemed to be a drawback. And to be fair, its not often that I can achieve that sort of speed. So, all in all, I think that this has been an unmitigated success. As my old dad used to tell me, "if you dont try, you can never succeed" and I think that this could be seen as a definite improvement to my bike. While off road, the steering seems to be more predictable, allowing me to get closer to the limit, making the whole experience more exhilirating, WHICH, FOR ME ANYWAY, IS WHAT ITS ALL ABOUT !


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## Bodhbh (6 Jan 2014)

Psycolist said:


> At speeds over 25mph while on road, there does seem to be a certain twitchy feeling to the steering that I had never noticed before. However, that is the only thing I have noticed that could be deemed to be a drawback.



I came it the other way and stuck a 29er wheel on the front of a 26er (456). The frame can supposedly take 100mm to 150mm suss forks. I had some 100m suss corrected rigid forks on the front, but didn't really like the twitchy handling, and the frame was too stretched out, front too low for me - I didn't really get on with it. The obvious thing would've been to stick a longer travel fork up front, but it seemed overkill as I mostly just ride bridlepaths and the like. So I stuck a 29er wheel up front and it was spot on - brought the bars a bit closer and slowed the handling a bit. I liked it so much I later tried to put a 80mm travel 29er fork up there, but....too much of a good thing - it was floppy up front and started pulling wheelies on climbs. It had a non-trival effect on the BB height too - quite a poke to find the floor.


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## Psycolist (6 Jan 2014)

Wowzer, wheelies on a climb must have been a bit of a shock. ! With this grotty rain and wind, I'm not getting alot of hours in the saddle at the moment, but I'm at the stage of getting a 'good' front wheel and a decent tyre selection, to accomodate differing conditions. I am very pleased with the set up, and glad that I tried it out. Just wishing the weather would pick up ! Like youself, I'm not into serious off roading, I just like to be able to go off piste and search out routes that a "roadie" wouldnt dare to venture along. I have lived in the same area for 30+ years, but since turning towards the muddy bits, i've been places, seen things and discovered villages I never even new existed, as well as getting a whole new lease of life towards cycling itself.


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