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Mixing Different bike wheels Smaller on front and Bigger on Rear(Quickly Explained)

Different wheel sizes on bikes are becoming common or you might think that they are but they have been common before as well Riders usually do this to top up one function of the bike like better rolling or more aerodynamic much like people mountain wider or narrower tires but this is completely different from that since we are talking mountain different tires for example mountain a 27.5 tire on the front on a bike that was set up to be run on 29″ wheels

this setup is less common and less used than the other setup like mounting a bigger tire in front and a smaller one on the rear and you might not even see it as much the reason for that is that it’s not quite common as the other setup and you might have seen it somewhere in the bike parks or if you travel than somewhere where there is some traffic on the trails.

To shorten the hassle and the quickest answer would be

You can use a smaller wheel in front and a bigger one on the rear (29″ in the rear and 27.5″ in front) on an XC bike only and on mild trails where you need more aerodynamics to roll your bike faster other than that you will break your wrists on any other bike or going downhill

If you ever used a bigger tire in front and used a smaller one in the rear or you have seen somebody do it you are bound to think would the reverse of that work and if so what could go wrong

and let me tell you everything except that you are riding very specific trails on a bike made for speed like an XC bike that excels on those kinds of trails and is made to be light to do that as well.

To understand what I am trying to say better take a look at a road bike

picture shows a road bike

Road bikes geometry and handlebars are made in a way that buries the rider into the bike making it more aerodynamic and reducing the air resistance that is the biggest counter or resisting factor in going faster on anything like a bike a car anything 

While you might not achieve that kind of aerodynamics on a mountain bike when you put a smaller tire upfront but you will closely resemble that but that’s bad for mountain bikes here’s why

How mounting a smaller wheel upfront on an MTB would Act :

Mountain bikes are made in a way that the rider sits in an upright position and that provides the rider with the most comfort and body weight balance on the bikes and makes it easier for the rider to have a perfect grip on the bike and helps him manage to throw his weight around as well

And installing a smaller wheel upfront will throw that balance because you would be forced to lean forward and alot more weight will fall over your wrists and hands while that is reverse otherwise and on mountain biking specific trails you would not be even able to do a loop without hurting your wrists I mentioned XC bikes as an exception because

normally you dont bring an XC bike on a downhill trail and remain mostly on gravel or mild trails but some people do try this mistake and well we all know how that turns around

but on gravel trails If you fit an XC with a lower tire upfront, it might do you some good in only aerodynamics of course nothing more than that  and that could mean something for them

But on Enduro, trail, and DH bikes it will turn into a disaster

Disadvantages of mounting a Smaller wheel on the front:

So far I have mentioned some of the advantages that you would get by putting a smaller wheel on an XC bike but there are some disadvantages to that as well and you should know that as well because it wouldn’t be fair otherwise so here’s a short list

  1. Hands going numb or you will get tired too soon
  2. neck soaring
  3. The rear tire will lose some grip and may skid on its own
  4. due to lowered front, you would be forced to lean in corners which can result in a crash
  5. making adjustments to the brakes and brake cables
  6. You will have to watch out for the Bottom bracket in the technical sections
  7. Maxing out front suspension too often

These are some of the obvious things that you will have to either fix watch out for or might even need to change.

You won’t be able to travel far although the bike might be a little bit faster the extra constant weight on your hands and keeping an eye on trails will become tougher with the time passage, you will constantly have to bend your neck around to see the line and bend in and bend out that would also put a strain on your back as well

Braking will surely get affected as well because due to the shifted weight managing rear will be more difficult because you are not riding on pavement but on trails but you can get away with that by using both brakes rather than using the front brake more which is obviously used more

I have already written a more optimal solution in case you are in a pinch and are looking for a solution  

The biggest concern is with cornering it will be alot harder to corner with the bikes geometry twisted this way you can end up crashing at high speed you will have to keep the leans perfectly otherwise you will lose balance on the bike

On the technical sections, you would need to make better line choices since your bottom brackets angle would also change and get lower as well so making the right depth calls would become crucial and you might need to think about where you are going more than you would normally do.

Adjustments you would need for this kind of SetUp :

Well we are through all the pros and cons and here is the adjustment that you would need to do, if you are you are in a pinch and you can’t find the right tires for your bike

  1. Brakes and brake cables
  2. Suspensions
  3. you would need to either lower your seat post, make it fixed or you would need to raise the handlebars

Brakes are brake cables are the easier one’s you would need to adjust them you would need slightly longer brake cables or adjust the existing ones so that they won’t get in the way when you are turning your bike

suspensions will be under more stress and you would find maxing them out quite often since there would be much more load on the front now and you might need to change washers more often as well

The most important or the biggest change you would need is a raised handlebar or a lower seat post in case you were using a dropper post you would need to cut it down to match the length of the handlebar so that you can slightly cut that steep angle and make more sense out of your bike

Or you could get slightly raised handlebars so that you dont throw yourself off bars when braking suddenly and that can happen very rapidly on this kind of setup depending on how low you are going to set up the front tire.

Closest Setups that could work with the given wheel sizes :

Now there are limitations and you can’t go far on them mounting a 29″ in the back and a 26″ wheel in front would not be a very good setup if you are calling for an accident the better setups would be with the minimal differences between the wheel sizes for example

  • Rear 29″ and Front 27.5″
  • Rear 27.5″ and Front 26″

These setups can work but you still have to be careful and make the bike as optimal for riding as you can as I have mentioned above you had like to close the gap as much as you can rather than forcing the wrong wheel combo because it would never turn out to be a good setup and making modifications to your bike just for a few rides will cost you alot.

if you are in a pinch I had to say wait it out or go for more optimal options like having a Bigger wheel in front and smaller in the rear that would work much more better than this kind of setup.

Conclusion :

Possibilities dont always mean success if you have the money to spare and experiment with different things sure try it but I would advise against it since a better version of it is already available in form of mountain bigger tire on the front rather than the rear.