I have an Eiger. Stock tires are 25 x 8-2 and 25 x 10-12.

If I increase the height to 26, will it hurt the power or performance?

 

You will loose some low end grunt, it will be the same as going a step higher in gearing. How much power your engines creates will decide on how much bottom grunt you loose.

 

You can always stick it in low ratio if you need more bottom end grunt. I find the Auto Eigers are a bit low geared anyway so, if it is an Auto, it might actually feel better.

 

Thank you both. It is an auto. I was mainly concerned with the additional stress turning the heavier tires may put on the transmission and drive train.

 

The most stress will be on the deive belt, but...unless your hill climbing or digging in sand, probably not an issue. If you feel it lugging down go to low for sure...

 

It depends somewhat on what type of tires you're going with. If its a lighter 26" tire like an itp mudlite at, they won't be a lot heavier than stock 25" tires. I doubt you'll notice much of a difference. If you're going with a much more aggressive tire with bigger lugs, then they definitely will weigh a lot more and you'll notice a drop in performance. I don't think you'll be in danger of breaking anything but it will rob you of a little power.