Calculating tire poke

[Captain Skip]

OK, let’s see if I figured this out the right way. I’m looking for new wheels and tires. I know what tires and size I want - Toyo Open Country ATIII in 285/70/17. The wheels are the sticky part. I want to try to keep the the tire poke out as close to stock as possible. I know the 285 is wider than the 245 stock tires. The 245’s are 9.5 inches wide while the 285’s are 11.25 inches wide so I’m adding 1 3/4 inches to the width….if you haven’t figured out by now I’m a math wizard to be able to figure that out…..

I just measured my existing setup with the stock 245’s. The wheels rim to the outside edge of the fender is 1 1/2 inch and the sidewall to the edge of the fender is 3/4 inch. That’s with the factory wheels that have a +44mm offset. I'm thinking of going with a +30mm offset - couldn't find any in +44 that I liked. (Shoutout to Matt from Discount Tire for a lot of guidance he gave me trying to narrow my search down.)

Using the online offset calculator and comparing the 245’s with the stock +44mm offset to 285’s with a +30mm offset shows the sidewall .25 inch closer to the inside and 1.35 inch farther out. If my math is correct this means that the tires will poke - at least the sidewalls - .60 inch outside the fenders. As this is the sidewall and not the tread I think I will be happy with that as with the tread not being as wide as the sidewall, I should have the edge of the tread just about even with the outside edge of the fender.

For those of you who fought and won the wheel calculation war does this make sense? Am I crunching the numbers correctly?

Thanks

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[blnewt]

Skip, here's my fit at the fender stock, then w/ 17x8.5 +10 on 295/70, so your Toyos would be 5mm in from mine at the same +10 offset. If you were to run that +30 you'd be about an inch inside from mine (20mm for the offset and 5mm for the narrower tire). I think you'd like that fender fit w/ the +30 but if you think you might be lifting it up a bit in the future you might want to go a bit less positive. With my +10 set I can run my Rubicon lift w/ 35s (since I also have a high fender kit). Just food for thought

 

[Captain Skip]

Skip, here's my fit at the fender stock, then w/ 17x8.5 +10 on 295/70, so your Toyos would be 5mm in from mine at the same +10 offset. If you were to run that +30 you'd be about an inch inside from mine (20mm for the offset and 5mm for the narrower tire). I think you'd like that fender fit w/ the +30 but if you think you might be lifting it up a bit in the future you might want to go a bit less positive. With my +10 set I can run my Rubicon lift w/ 35s (since I also have a high fender kit). Just food for thought

Thank the photos are a big help.

 

[blnewt]

Here's a couple more to give you an idea from more angles

 

[Discount Tire]

Thanks for the shoutout, Skip! Always happy to help.

You're math looks solid. I estimate the poke will be between 1/2" to 3/4" outside of the fender with the 285's mounted. Tires, much like shoes, can measure differently even in the same size which is why I provided a range.

 

[Some Random Guy]

Are you worried about inside clearance at all? I’m not sure if you flex it out very often. Lift kits usually have a maximum backspacing to avoid tire rub on fenders or control arms. I’m not sure how much room there is at stock.

 

[Captain Skip]

Are you worried about inside clearance at all? I’m not sure if you flex it out very often. Lift kits usually have a maximum backspacing to avoid tire rub on fenders or control arms. I’m not sure how much room there is at stock.

Inside is about 1/4" closer than stock. I'm not worried about that as I won't be lifting it at all. The Commander in Chief is vertically challenged (don't you dare call her short!) and has limited movement with her legs because of a hip issue so I'm pushing things going from a 245/75 to a 285/70 tire. My off roading is on Class VI roads, forest trails and things like that. I'm not into rock crawling so I don't envision going full flex on anything if I can help it. I appreciate the input though!

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