2004 Ambassador RR4R Increased Tire Size Fit?

[Smithj]

Hello...I am trying to improve the ride on our 2004 HR Ambassador with the RR4R suspension. I have read many RR4R posts on the forum which led me to install the Source Engineering control arms and the REK upgrade with Bilstein shocks (back in 2015). I have also adjusted my ride height to Source Engineering specifications. I discussed the options with Jim at Source Engineering and based on his recommendation I am planning to increase my front steer tires (not the drive tires) from the current 275/70 R22.5 to 295/80 R22.5.

I have an appointment Monday morning to make the change and I would like to know if anyone with an RR4R chassis (Jim says the Cayman has the same chassis) has increased their tire size and could share their experience?

Thanks.

[jacwjames]

Not sure how much clearance you have to up size your tire. Here's a website that allows you compare the difference in size. 'https://tiresize.com/comparison/
Width and diameter might cause a problem, but I know a lot of people upsize so you might be OK

[Smithj]

Thanks Jim. I used a similar site to compare and the width increases from 10.8" to 11.6", the height increases from 37.7" to 41.1" and most importantly the sidewall increases from 7.6" to 9.3" for a 22.4% increase. I will test the fit tomorrow as the tire shop has promised to work with me to make sure the fit is ok.

I was concerned about running a larger steer tire than drive tire, but Source Engineering and the tire shop both say it is ok? The new tires will reduce the current 18 ply tire to a 16 ply and also allow me to lower my tire pressure on my 10,000 lb front axle to 85 psi.

Theoretically, the new tires should help to take the "harshness" out of the front axle? I am concerned about the appearance of the tire combination, but I am willing to trade appearance for performance. Hopefully someone that has made a similar switch will let me know how it worked for them.

[Iceclimber]

I have that exact year chassis and wonder how many dollars you can throw at something that is only going to perform to a certain point - meaning maybe it's only going to do what it can do - from a pure engineering perspective. My personal opinion is the RR4R is literally half what it should be, (shocks and bags) but it's in the driveway now.

[Smithj]

I replaced the 18 ply 275/70R22.5 steering tires with 16 ply 295/75R22.5 tires and it appears to have softened the ride significantly. Combined with the Source Engineering upgrades the ride is "acceptable".

Thanks.