Upgrade Tire Size Forums › Mountain Bike Forum › Upgrade Tire Size Tweet Add to Flipboard Magazine. Tagged: tire, Tire Size, tire width, tires, tyre, tyres Viewing 2 reply threads Author Posts April 24, 2017 at 10:05 #213622 dwirtz I want to upgrade the tire size on my Trek. I have 29″ with 2.20. What is the biggest I can go without change the fork. 2.40? April 24, 2017 at 10:10 #213623 Jeff Barber Chances are your fork has plenty of clearance for 2.4 and maybe even bigger. Most do. Which Trek are you riding? If you can post a photo of the rear clearance we might be able to get a better idea. April 24, 2017 at 12:03 #213653 dwirtz I have a Trek Mamba. I looked at taking a picture of the rear tire and it is already tight on the lower fork already. Not sure if anything bigger will fit on the rear. I am going to order a 2.40 for the front Any thoughts on a brand? Author Posts Viewing 2 reply threads RELATED TOPICS Topic Voices Posts Freshness Tubeless tyres will not bead Started by: 22jeffers in: Mountain Bike Forum 6 8 5 months, 3 weeks ago Sunspot To heavy for 28 spoke wheels? Started by: OGD1 in: Mountain Bike Forum 2 2 5 months, 3 weeks ago Bike Nerd 2.35 or 2.6" tyres? Started by: crembz in: Mountain Bike Forum 7 21 1 year, 2 months ago dlawson Tyre width Started by: Sydney Rider in: Mountain Bike Forum 4 5 2 years, 1 month ago FredCook Tubeless; When to take action on tyre damage? Started by: Jonnorth in: Mountain Bike Forum 2 2 2 years, 8 months ago Head Over Handlebars You must be logged in to reply to this topic.