Traction XB Coupe

drcoupe · 15-05-2011, 11:26 PM

G'Day

I am a drag racing novice about to go down and give it a crack but I am struggling to get the power down with my current street tyres (295/60/15). I have decided to buy some Mickey Thompson ET Streets to help out either 275/60/15 or 315/60/15, I have an XB coupe so I have a bit of room however the 315's may be tight and it would probably be easier just to go the 275's. Does anyone know what benefits there will be persisting with the 315's over the 275's or will the difference be negligible? Also are there any tyre pressure recommendations and as I am buying a couple of new 15 x 10 rims for the M/T's does it matter what rims I buy ie: is there any benefit buying a particular rim type? Lastly I have GTHO springs on the back and Koni adjustable shocks should I be aiming to soften the shocks to assist with traction?

Thanks for your help.

DR

xagsjoe · 16-05-2011, 12:14 AM

You Auto or manual? What's HP is your engine making, trans, stall if auto?

Any perticular reason to stick with a radial over a slick? Reason I ask is it takes some work getting a radial of any type to hook hard.

The first thing you need are caltrac bars or oztraks, at the minimum some slapper bars. Checkout the link below.

http://www.hotrodsandhemis.com/Traction.html

Some 90/10's up front with 6cyl springs will work fine in most apps. A 5 leaf spring pack@ around 200lb rate for the rear is about right.

There are lots of things you can do bit radials just make it harder.

drcoupe · 16-05-2011, 11:29 AM

Thanks for the advice xagsjoe.

I want to keep the car as a street car but the main reason for not going slicks is that I have been told I need front runners on the front. Apparently you shouldn't mix or are not allowed to mix radials on the front with slicks on the back? I have a shift kitted C4 (Hardened input shaft, billet servo, 6 gear planetary set), 3500 Stall and 3.5:1 nine inch. Power is 480 Hp and 440 ft/lbs at the flywheel (standard stroke 351) but I have just ordered a Nitrous Express Kit to give it a bit more kick.

DR

XB GS 351 Coupe · 16-05-2011, 02:21 PM

With those diff gears the 28" tyres will be too tall, it would be like running a 2.75 diff, you should be looking at 26" tyres, otherwise your gearing will be all wrong (from personal experience in my own coupe).

The 315's will not fit with standard wheel arches.

I have some brand new 28x12.5-15 Mickey Thompson Sportsman Pro's for sale same compound as slicks with wrinkle wall construction, will definitely fit coupe wheel arches as I used them to set mine up, retail $680 a pair, I can do them for $500 brand new, never been driven on, but have been fitted to rims before.

JG33RD · 20-05-2011, 06:49 AM

Quote:

Originally Posted by drcoupe

Thanks for the advice xagsjoe.

I want to keep the car as a street car but the main reason for not going slicks is that I have been told I need front runners on the front. Apparently you shouldn't mix or are not allowed to mix radials on the front with slicks on the back? I have a shift kitted C4 (Hardened input shaft, billet servo, 6 gear planetary set), 3500 Stall and 3.5:1 nine inch. Power is 480 Hp and 440 ft/lbs at the flywheel (standard stroke 351) but I have just ordered a Nitrous Express Kit to give it a bit more kick.

DR

They don't have to be the front runners, I bought some "rags" for mine and fitted them to the standard 6" rim. If you have 480hp now and going to use N2o then I think you are going to need something that will stick.

TICK4D · 20-05-2011, 06:50 PM

If you run slicks on the back (or front for FWD) the other tyres must be a cross ply tyre, radials are not allowed.
As XAGSJOE said check how many leaves you have, as you want it to bite, just trying to buy a bigger tyre is not the answer, you need the car to transfer the weight for a good hook up.

drcoupe · 20-05-2011, 08:35 PM

Thanks for the comments fellas. I am going to get a couple of 275/50 ET Streets on Monday and look at some slicks for next season. Any suggestions on tyre pressure for the ET Streets? I will have a look at the springs Tick4d but in the meanwhile I assume adjusting the shocks a bit softer will help?

DR

4VCLEVO · 23-05-2011, 11:23 PM

Quote:

Originally Posted by drcoupe

Thanks for the comments fellas. I am going to get a couple of 275/50 ET Streets on Monday and look at some slicks for next season. Any suggestions on tyre pressure for the ET Streets? I will have a look at the springs Tick4d but in the meanwhile I assume adjusting the shocks a bit softer will help?

DR

Did you end up getting ET streets or ET street radials? If you got the ET streets, you will still need front runners.

ET street radials
http://www.mickeythompsontires.com/s...ETStreetRadial

ET streets
http://www.mickeythompsontires.com/s...?item=ETStreet

JG33RD · 21-05-2011, 03:34 PM

I haven't used the ET streets before but I know a bloke who has and he went as low as 15psi, not sure if that's of much help to you, maybe start about 18 and see how it goes.

dieseltrain79 · 21-05-2011, 07:41 PM

ET Streets , i start at 18psi and drop 1 psi to suit the track if its not sticking . Dont go any lower than 14psi though .

Have gone 1.60 in the 60' on a pair of 255/50/16's on my car with some more left in it . 28-32psi on the street with them .

drcoupe · 21-05-2011, 08:42 PM

Thanks fellas 18 psi it is then.

DR

XB GS 351 Coupe · 22-05-2011, 08:19 PM

Start on 18psi and keep an eye on the pressure after each run as it will go up, and you will need to let air out (this was in summer though).

I ended up with 16psi in the same tyres, and was OK.

Just keep in mind that the Street Radials are a LOT harder to control and that they are a LOT harder on the driveline than slicks, or cross ply like the Mickey Thompson Sportsman Pro, as they absorb less shock as there is no wrinkle wall to reduce the impact on the driveline and assist in hooking the car up.

Here are the Sportsman Pro next to the 295/50-15 T/A's:

Here they are on my coupe for a trail fit:

No rubbing with the correct offset.

drcoupe · 25-05-2011, 09:44 AM

Thanks for the pics XB GS 351 Coupe, it makes sense what you mean about the slicks having less stress. You have to love being able to stick big tyres under the rear without any hassle though, thanks for the pics. I did get the radials 4V Clevo and I noticed the difference straight away in grip. I am heading down tonight to see how they go.

DR

4VCLEVO · 25-05-2011, 09:40 PM

Quote:

Originally Posted by drcoupe

Thanks for the pics XB GS 351 Coupe, it makes sense what you mean about the slicks having less stress. You have to love being able to stick big tyres under the rear without any hassle though, thanks for the pics. I did get the radials 4V Clevo and I noticed the difference straight away in grip. I am heading down tonight to see how they go.

DR

Great, let us know how you go as I am going through the same delema of weather to go radials or not.

drcoupe · 28-05-2011, 09:48 PM

The M/T ET Streets worked well, wish I could say the same thing about my brand new High Energy Sump. %$#% thing split and I didn't get a chance to get a decent run in. I enjoyed heading down just to push it off the track and go home again....

DR

xdclevo · 29-05-2011, 01:58 PM

Quote:

Originally Posted by drcoupe

The M/T ET Streets worked well, wish I could say the same thing about my brand new High Energy Sump. %$#% thing split and I didn't get a chance to get a decent run in.

Yep, i had same dramas with the crappy High Energy sump. Leaked from new, then cracked a few years later in different spot alltogether.
Sorry to hear mate.

drcoupe · 29-05-2011, 08:59 PM

What did you replace it with XD Clevo? I am looking for alternatives as I am not going to put one back on, not worth the risk.

DR

JG33RD · 29-05-2011, 08:09 AM

That sux, have heard some less than average comments about those sumps. Search through the clevo threads and you will see what I mean. My advice would be to do some research on what's good and what you can afford then change it otherwise you will be forever repairing it. If your handy with a mig maybe have a go at making your own.

drcoupe · 29-05-2011, 12:53 PM

A bit off topic but I am after some advice on diff gearing in the Driveline section if anyone can help.

DR

JG33RD · 15-06-2011, 10:55 PM

Did you find a better pan DR?

drcoupe · 30-06-2011, 04:42 PM

Hey JG33RD

Recommendation was an ASR sump, motors out and the sump is supposed to be arriving this week. Also changed to 3.89 gears with 31 spline axles and fitting a NX nitrous kit with progressive controller so we will see what happens in Sept.

DR

drcoupe · 07-11-2011, 12:44 AM

G'Day

Finally got a few runs in with a best of 12.475 secs @ 112.07 mph, 1.980 sec 60', 5.321 sec 330', 8.069 sec 660', 10.458 sec 1000'. Without nitrous and safe tune.

DR

u2canb12 · 07-11-2011, 09:57 AM

Quote:

Originally Posted by drcoupe

G'Day

Finally got a few runs in with a best of 12.475 secs @ 112.07 mph, 1.980 sec 60', 5.321 sec 330', 8.069 sec 660', 10.458 sec 1000'. Without nitrous and safe tune.

DR

Nice!, gotta be happy with that? When do you try the Nitrous?

drcoupe · 07-11-2011, 06:29 PM

G'Day UCANB12

I want to knock the rev limiter up and play around with the tuning to see if I can get into the 11's first then I will give the nitrous a crack.

DR

JG33RD · 25-11-2011, 01:19 AM

Quote:

Originally Posted by drcoupe

G'Day

Finally got a few runs in with a best of 12.475 secs @ 112.07 mph, 1.980 sec 60', 5.321 sec 330', 8.069 sec 660', 10.458 sec 1000'. Without nitrous and safe tune.

DR

Good results, did you end up with 28" tyres and what rpm were you pulling over the line with those gears? I have yet to change mine but have run a 12.61@108 with 28's and 3.7 gears with a 5000 stall, only getting to about 5600 over the line, peak hp on my engine is 6800 so just curious bout your setup, again congrats on the passes and bring on 11's

drcoupe · 14-12-2011, 04:18 PM

G'Day JG33RD

I am around 5800-5900 over the line, can't remember my tyre profile offhand but I am running a 3500 stall and I am also at 6800 peak but I was changing at 6000 last time as I seemed to be breaking down around 6200-6300. My rev limiter was set at 6500 and I have been told that MSD's can start to break down a couple of hundred revs below.

DR

JG33RD · 14-12-2011, 05:12 PM

Quote:

Originally Posted by drcoupe

G'Day JG33RD

I am around 5800-5900 over the line, can't remember my tyre profile offhand but I am running a 3500 stall and I am also at 6800 peak but I was changing at 6000 last time as I seemed to be breaking down around 6200-6300. My rev limiter was set at 6500 and I have been told that MSD's can start to break down a couple of hundred revs below.

DR

Thanks for that, gives me a bit of an idea of what I can expect, rev's, over the line with the new gears. Good thing the MSD's are easy enough to change rev limit, have heard the ones you can change from the cab are the go. I have mine set at 7000 with the shift light coming on at 6700, by the time I change it bangs the limiter for a split sec.

dirty · 24-11-2011, 10:25 PM

Good work, a way to go from 12.4 to 11's, good luck with it all!

drcoupe · 15-12-2011, 05:12 PM

G'Day JG33RD

I went down last night with a couple of degrees more timing, up a couple of jet sizes removed the nitrous plate for a tapered 1" spacer and removed the aircleaner and got a 12.11 @ 114.21 MPH, 1.918 60', 5.133 330', 7.805 660' and 10.135 1000'. Everything still under the bonnet and find that 6000 RPM is best for shifting. I was loading up to 2500 RPM but found I was losing traction going up to 3000 RPM so if I can sort this out I am getting close to 11's.

DR

JG33RD · 15-12-2011, 11:19 PM

That's senssational DR

, excellent time, although your 60' is as bad as mine, get this sorted and your running 11's consistant. Check out my thread "need help with 60's", got some good advise from people here, not sure if removing the air cleaner is a good option but if your comfortable with it then all good. The 6000 shift change doesn't suprise me, I was talking to someone who said "you have to find what the car likes" in relation to shifts, I thought best shift point was after peak HP, maybe there is more to it

Anyway congrats on the 12.1 and hopefully I can crack an 11 before you lmao