[Drsagacity]

Originally Posted by Black Hole

OK - I'm back on the e85 train; I have 2 other tuners in the area to check out. Now, back to the drag radials...LOL.

Yes please! It would be really nice if anyone could point to experience from real testing.

1. What MPH difference do you see in the quarter mile when running 20in DR’s compared to running a 17in DR.

2. What about ET?

I suppose I will do the experiment myself if nobody else has real data for comparison.

[KingLT1]

Originally Posted by Black Hole

The tuner was very adamant regarding the e85 - indicating his problem with it was that the flex fuel sensor would not adjust timing, only the fueling, so detonation (and subsequent "blown" motor) was not only possible - he had seen it happen many times. Perhaps those folks are the remaining 10% @danhr alluded to.


Every time I check on the ship status of the new MTs, they are delayed even further. I wonder if anyone has even been able to get a set yet; i.e. are they delayed in entirety or is it that MT can;t keep up with demand.

It sounds like your tuner is referencing older LS based ECM's that do not have a Flex Fuel spark table in the ECM...not the case with the newer Gen5 stuff.

The Gen5 ECM's have both a Stoich and flex fuel spark table(That need to be setup correctly prior to running E) which are both based off of ethanol content. Once the FFS sends a specific frequency to the ECM telling it basically how much E content is in the fuel, these 2 tables are referenced to adjust the timing and fueling correctly.

[Black Hole]

Even 0-60 or 1/8 mile differences would shed some light on the best path to take for 20" vs 17".

[Snowblind]

I am not exactly clear on what you guys are trying to find out. A 28" DR tire (whether its on a 20-18-17-16 or 15" wheel) will net you the same result, provided traction is taken out of the equation. Your car is still rolling on a 28" regardless.

[kttxz06]

Originally Posted by Black Hole

Goals: Effective street performance, meaning more concerned with 0-60 than top speed; effective drag strip performance, leaning toward 1/8 mile ET. Low mileage daily driver who likes to go straight; not worried about "twisties."

Question: Does anyone have experience using 20" drag radials AND 17" or smaller Drag Pack for comparison so I can learn the following -
1. For a bone stock vehicle, are the 20's up to the task of holding full throttle off the line or do I need a smaller diameter wheel?
2. For a slightly modded vehicle (+50 hp), are the 20's up to the task of holding full throttle off the line, or do I need a smaller diameter wheel?

I currently run Toyo R888R comp tires but they are not meeting my needs. I am looking at the MT ET Street in the 285/30/20 or picking up 17" or smaller wheels (the Weld 15's look especially nice, though pricey) and MT ET Streets to match.

Let's assume track prep and DA conditions are "average." I appreciate your insights. Thanks in advance!

R888R's aren't holding a +50 hp bump. Makes no sense. Those tires grip up until the 750 hp range, then they start cutting loose.

[Stefano]

Going back to the OPs original question...... the appropriate DRs on 20s will hook hard enough to just about pull the wheels and will hook way beyond stock HP levels. I have run 10.30 -10.40s with 1.60fts with 20s all the way around.

[Stefano]

Also, I run e85 : )

[ULTRAZLS1]

17 inch wheels all around will save you ~80 lbs. In rotating weight. That’s worth at least a tenth. Probably two. And that’s with my cheap heavy race stars

[driven2exceSS]

Originally Posted by Stefano

Also, I run e85 : )

Funny, I like the humor behind that!

[Drsagacity]

Originally Posted by Snowblind

I am not exactly clear on what you guys are trying to find out. A 28" DR tire (whether its on a 20-18-17-16 or 15" wheel) will net you the same result, provided traction is taken out of the equation. Your car is still rolling on a 28" regardless.

I do not believe that is the case because of different sidewall size and because of the weight difference for rotating mass...so, I am interested in empirical evidence to understand what I am giving up if I run on 20’s vs 17’s.

[Drsagacity]

Originally Posted by Stefano

Going back to the OPs original question...... the appropriate DRs on 20s will hook hard enough to just about pull the wheels and will hook way beyond stock HP levels. I have run 10.30 -10.40s with 1.60fts with 20s all the way around.

Stefano, what mph are you trapping? You might have the best datapoint.

[danhr]

Originally Posted by Snowblind

I am not exactly clear on what you guys are trying to find out. A 28" DR tire (whether its on a 20-18-17-16 or 15" wheel) will net you the same result, provided traction is taken out of the equation. Your car is still rolling on a 28" regardless.

It's not the tire height that effects, even if you get both to dead hook, it's the reduction in rotational weight.
20" rear wheel = 32.30 lbs
20" nt05 tire 275 35 20 = 30 lbs

So a 20" drag radial setup weighs ~128 lbs

17x9.5 racestar = 20 lbs each
275 50 17 drag radial = 29 lbs (it's a little taller than the 275 35 20).

17 drag radial setup= 98 lbs

So that's a difference of 30 lbs. The general rule of thumb is that 1 pound off the wheel is worth 3 off the car.... so it's like taking 90 pounds out of your car. And the rule of thumb is that 100 lbs is worth a tenth.

That's obviously just a rule of thumb... weight effects each car differently. So since one person on this forum cut .2 off their et, doesn't mean you will.

If you want to go really hardcore... a 15x10 wheel weighs in around 10 lbs, and a 28x10.5x15 tire is again 29 lbs. That's 78 lbs. So that's like cutting 150 lbs from the inside of your car.

[parish8]

Originally Posted by danhr

It's not the tire height that effects, even if you get both to dead hook, it's the reduction in rotational weight.
20" rear wheel = 32.30 lbs
20" nt05 tire 275 35 20 = 30 lbs

So a 20" drag radial setup weighs ~128 lbs

17x9.5 racestar = 20 lbs each
275 50 17 drag radial = 29 lbs (it's a little taller than the 275 35 20).

17 drag radial setup= 98 lbs

So that's a difference of 30 lbs. The general rule of thumb is that 1 pound off the wheel is worth 3 off the car.... so it's like taking 90 pounds out of your car. And the rule of thumb is that 100 lbs is worth a tenth.

That's obviously just a rule of thumb... weight effects each car differently. So since one person on this forum cut .2 off their et, doesn't mean you will.

If you want to go really hardcore... a 15x10 wheel weighs in around 10 lbs, and a 28x10.5x15 tire is again 29 lbs. That's 78 lbs. So that's like cutting 150 lbs from the inside of your car.

That 1lb is worth 3lbs is a little high. Here is a thread with some links to the math. https://www.camaro6.com/forums/showt...ght=Rotational

It is closer to 1lb is worth ~1.6-1.7lbs when talking about rim/tire combo. Still a huge deal to drop wheel weight.

[Snowblind]

Originally Posted by Drsagacity

I do not believe that is the case because of different sidewall size and because of the weight difference for rotating mass...so, I am interested in empirical evidence to understand what I am giving up if I run on 20’s vs 17’s.

It only makes sense that this thread would steer towards weight reduction and rotating mass, that's obvious. I was just trying to answer the OP's question in post 1 and your follow up questions in regards to 20 vs 17 inch DR's and traction. If your budget allows it then the 17 would be the better long term choice, both in tire size options and if you choose to improve the performance of your vehicle moving forward...plus the benefit of WR

All I was stating is that a 20" DR can perform the same task as a 17 if lack of traction is not a factor. I'm not trying to toot my horn, but I have made over 175 passes in 2 1/2 seasons and have made many passes on both setups, I think it's safe to say I have more experience with both setups more than anyone on here. A 1.58 I believe is the best 60' I made on a 20 before I went to a complete 17" drag pack. I am now in the 1.4's but I have bumped up the mods so I cannot give you an apples to apples comparison, I still have my 20's sitting in the garage...maybe I'll swap them one day and see if their is a difference.

I hope this helps, good luck with whatever route you choose. I look forward to your results.