Do SCORE and BITD limit wheel diameter sizes???

Chris Tobin

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Why do you think you need bigger brakes than a trophy truck? Sure, your truck weighs more than a trophy truck, but unless you sink MAJOR bucks into it, you won't be going nearly as fast. I'd be much more concerned with spindles and hubs than brakes. If you haven't priced those out, brakes are the least of your concerns.

More braking capability is always a good thing. I know I will come up far short of a TT in suspension capability, but I'd like to improve whatever areas I can... Improving the brakes is an area that is likely within my means. So I am looking for input on the other areas that will be impacted by the move to the larger brake combo, namely the wheels and tires. Honestly, I was hoping that the spindles and factory 3/4-ton hubs will be strong enough...

You will have a very small side wall with a 37/20, heavy vehicle= pinch flats.
Everybody would love to run a bigger brake package, but you sacrifice that with a bigger wheel and more likely pinch flats.

That was one of my major concerns with the 37/20... and that is why I was looking for input from anyone who has run that size combo on something other than a mall crawler... At the shows and events I regularly cove guys are running 22s with 35s and I hate the low profile MT tire look and know that would be pushing it way too far.

Looking at the basic math a 35/17 combo has about 9-inches of sidewall while a 37/17 combo has about 10-inches of sidewall and a 37/20 combo would yield about 8.5-inches of sidewall. It would sacrifice about 1.5-inches of sidewall from my current 37/17 combo, but would only be 0.5 inches worse than a 35/17 combo which a lot of people run so would it really be that bad???

I obviously don't have the money to throw away to experiment so I was hoping someone else already has...

Thanks again for the continued comments, everything will help me come to a conclusion...
 

Dirty Harry

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Where are you planning to run 37s on 20s Chris? I think for recreational use they will be fine, it won't be until you are pushing hard in a race environment that I would expect pinch flats to become an issue.
 

Chris Tobin

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Where are you planning to run 37s on 20s Chris? I think for recreational use they will be fine, it won't be until you are pushing hard in a race environment that I would expect pinch flats to become an issue.
Ultimately, what we want to do with the truck is drive from here in TN out west, run a desert race then drive it back home to TN...

We wouldn't be racing to win, but want to finish whatever race we enter... Probably do a Texana Ranch race first then maybe Vegas to Reno and ultimately do the Baja 1000 at some point...
 

Chris_Wilson

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I guess it depends on how fast or slow you are going to go but as a general rule if you want to go fast you need 10" of sidewall to deflect over rocks without bending rims or getting pinch flats. That's for desert racing. You can get away with less in short course.
 

Chris Tobin

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Your factory hubs won't hold up; there is nothing in a GM front end that will hold up offroad.
The hubs are one of the only things left that are factory... The diff is an ARB, the gears are G2, the diff housing is factory but the center axle disconnect is deleted and replace with a new housing and new internal shafts that are larger and stronger and finally the CV axle shafts have been replaced with RCV's Ultimate Axles. The spindles are aftermarket cast spindles that came with the Pure Performance suspension system and yes the hubs are factory 3/4 or 1-ton hubs.

I'm sure none of it would hold up to TT attempted speeds, but I was hoping they would work for 14-inch front travel speeds...
 

Chris Tobin

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I guess it depends on how fast or slow you are going to go but as a general rule if you want to go fast you need 10" of sidewall to deflect over rocks without bending rims or getting pinch flats. That's for desert racing. You can get away with less in short course.
So by that rule even a 35/17 would be a no go and a 37/17 combo would be the smallest combo I could go with on the truck...
 

BigBlue&Goldie

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The hubs are one of the only things left that are factory... The diff is an ARB, the gears are G2, the diff housing is factory but the center axle disconnect is deleted and replace with a new housing and new internal shafts that are larger and stronger and finally the CV axle shafts have been replaced with RCV's Ultimate Axles. The spindles are aftermarket cast spindles that came with the Pure Performance suspension system and yes the hubs are factory 3/4 or 1-ton hubs.

I'm sure none of it would hold up to TT attempted speeds, but I was hoping they would work for 14-inch front travel speeds...

Realistically, with that setup you probably won't be going much faster than a Raptor. I wouldn't worry about bigger brakes.
 

Chris_Wilson

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So by that rule even a 35/17 would be a no go and a 37/17 combo would be the smallest combo I could go with on the truck...

Correct a 35 on a 17 will either bend rims or get pinch flats if you are going fast on modern desert race tracks.
 

Chris Tobin

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Realistically, with that setup you probably won't be going much faster than a Raptor. I wouldn't worry about bigger brakes.

Honestly, I didn't expect to go much faster in the rough, but I imagine I will be considerably faster in smoother sections since I will have probably double the horsepower and something like triple or quadruple the torque! AND I will probably weigh more, so I figured the bigger brakes wouldn't hurt...

Correct a 35 on a 17 will either bend rims or get pinch flats if you are going fast on modern desert race tracks.

But then again, if I am getting more flats, it would hurt...

Decisions, decisions, decisions...
 

bobsson

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More braking capability is always a good thing. I know I will come up far short of a TT in suspension capability, but I'd like to improve whatever areas I can... Improving the brakes is an area that is likely within my means. So I am looking for input on the other areas that will be impacted by the move to the larger brake combo, namely the wheels and tires. Honestly, I was hoping that the spindles and factory 3/4-ton hubs will be strong enough...



That was one of my major concerns with the 37/20... and that is why I was looking for input from anyone who has run that size combo on something other than a mall crawler... At the shows and events I regularly cove guys are running 22s with 35s and I hate the low profile MT tire look and know that would be pushing it way too far.

Looking at the basic math a 35/17 combo has about 9-inches of sidewall while a 37/17 combo has about 10-inches of sidewall and a 37/20 combo would yield about 8.5-inches of sidewall. It would sacrifice about 1.5-inches of sidewall from my current 37/17 combo, but would only be 0.5 inches worse than a 35/17 combo which a lot of people run so would it really be that bad???

I obviously don't have the money to throw away to experiment so I was hoping someone else already has...

Thanks again for the continued comments, everything will help me come to a conclusion...
My truck likely weighs half of what your truck does as its 4k pounds ready to run. That weight difference is really going to affect how likely you'll get a pinch flat.
 

TRON3000

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Please tell me you are going to upgrade the entire steering system. This build sounds like you will struggle to drive home from a race. Sorry but that pure performance kit is designed for moderate off road use, not race abuse. If the kit doesn't break the steering will for sure.
 

Chris Tobin

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Please tell me you are going to upgrade the entire steering system. This build sounds like you will struggle to drive home from a race. Sorry but that pure performance kit is designed for moderate off road use, not race abuse. If the kit doesn't break the steering will for sure.
As of now the steering is using the stock 2500 HD steering box along with new outer tie rod ends and a solid center drag link with inner heim joints with solid mounts to the tie rod ends and a stock pittman arm. The Idler arm is being replaced by a Kryptonite arm and I will add the PPE steering braces as needed...

What else do you recommend for upgrading the steering???

I can say that while most Duramax trucks toe-in pretty hard when sled pulling and doing boosted launches in drag racing that mine stays completely true and straight and it is one of the few GM IFS trucks I have seen or shot that does not seem to deflect at all under boosted launch conditions.

What else if anything would you recommend to further upgrade the Pure Performance kit/parts?

Thanks for any input and suggestions!
 
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