Archived

This topic is now archived and is closed to further replies.

tnlmaverick

tire size (height)

Recommended Posts

What is the height difference, if there is any, between a 20.8 X 38 tire and a 18.4 X 38 tire? I am running 20.8 X 38 tires but would like to eventually switch to 18.4 X 38 tires. I would like run the current 20.8 x 38s until they are worn further and then switch to 18.4 X 38s. I would like to get a set of duals to run before spring but if possible would like to get 18.4 X 38 if the heights are the same or close.

Share this post


Link to post
Share on other sites

18.4X42 are the same height as a 20.8X38 the 18.4X38 is about 3 to 6 inches shorter

Share this post


Link to post
Share on other sites
18.4X42 are the same height as a 20.8X38 the 18.4X38 is about 3 to 6 inches shorter

Agreed. We currently have a 7130 Magnum in the shop, has 18.4-42 drive tires, and 20.8-38 duals on the rear, and the two have about the same height. I want his duals, but thats a different subject altogether! :wacko:

Share this post


Link to post
Share on other sites

Hi-jacking the thread for no reason 20.8-34's arn't the same height as 18.4-38's are they? I would think they are shorter.

Never mind Firestone says they are shorter, man I am smart! maybe

Share this post


Link to post
Share on other sites

What are u planing on. thàt u want to make this switch and what model tractor are u going to do this for is it FWD. I've do tire swaps many times for diffrent apps just was going to offer my thoughts

Share this post


Link to post
Share on other sites

Overall diameter 20.8 x 38=79.6", overall diameter 18.4 x 42=78.8", overall diameter 18.4 x 38=74.8". Therefore ground to axle height difference only .4" (1/2 of .8") between 20.8 x 38 and 18.4 x 42, but is 2.4" different (1/2 of 4.8") between 20.8 x 38 and 18.4 x 38. If you run duals with 20.8 x 38 and 18.4 x 38, you definitely want to run the 20.8s on the inside and the 18.4s on the outside.

Harold H

What is the height difference, if there is any, between a 20.8 X 38 tire and a 18.4 X 38 tire? I am running 20.8 X 38 tires but would like to eventually switch to 18.4 X 38 tires. I would like run the current 20.8 x 38s until they are worn further and then switch to 18.4 X 38s. I would like to get a set of duals to run before spring but if possible would like to get 18.4 X 38 if the heights are the same or close.

Share this post


Link to post
Share on other sites

Another thought to through you off is that different tire company's tires (same tire size) is actually differen't, not by much but it can differ from 1-2in. at times, go to different companys web-sites and look at the tire data, the rim width will change height as well. If this is a MFD tractor you have to pay close attention to front tire size to keep the gear ratios the same (correct).

Share this post


Link to post
Share on other sites
Hi-jacking the thread for no reason 20.8-34's arn't the same height as 18.4-38's are they? I would think they are shorter.

Never mind Firestone says they are shorter, man I am smart! maybe

Shawn, Im going to say that they are the same size. A buddy of mine put a set just about new 20.8-34's on his 4430, and they were pretty close to the same height as his 18.4-38's(about the same % of tread) on his 200 AC.

Share this post


Link to post
Share on other sites

What is the biggest problem with running taller tires as a dual rather than on the inside? It wouldn't make any difference would it?

Share this post


Link to post
Share on other sites

What is the height difference, if there is any, between a 20.8 X 38 tire and a 18.4 X 38 tire? I am running 20.8 X 38 tires but would like to eventually switch to 18.4 X 38 tires. I would like run the current 20.8 x 38s until they are worn further and then switch to 18.4 X 38s. I would like to get a set of duals to run before spring but if possible would like to get 18.4 X 38 if the heights are the same or close.

I had the same problem on a tractor. I went with step up rims and 18.4X 42 on the tractor, and kept the 20.8X38 duals...they are the same height.

...................Mark

Share this post


Link to post
Share on other sites

What is the biggest problem with running taller tires as a dual rather than on the inside? It wouldn't make any difference would it?

It does make a difference. The bigger tire will hit the ground with more force, thus taking more weight, and exerting more pull. Basic physics says that if you are removing a stubborn nut, and have X amount of force, and you need more, put a longer pipe on, and you can increased pressure on the nut with the same force. It works that way on your tractor rear end as well. That is why in the manual for any modern tractor it will say that with tires set wide you should reduce three point load or drawbar pull. I hope I explained that well enough. :)

Share this post


Link to post
Share on other sites

Never run a larger tire on the outside. Puts a lot of unnecessary strain on gear train, dual hubs and bolts. In fact, with same size tires run a little less air pressure in dual for this same reason.

Share this post


Link to post
Share on other sites

There's been many an axle broken bcause of excess pressure from the outer dual. Eason

Share this post


Link to post
Share on other sites