Team Chevelle banner
  • Hey everyone! Enter your ride HERE to be a part JULY's Ride of the Month Challenge!
1 - 17 of 17 Posts

·
Registered
Joined
·
3,697 Posts
Discussion Starter · #1 ·
This is for a street only, 69 el Camino, with a modern Delrin bushed suspension front and rear.

I'm looking at tire sizes, my wheels are 15x7 4.25 back space, Series 62, stock looking wheels..

I presently have 255/60r15 (9" width) front and 275/60r15 (9" width) rear (I know! haha)...

The 7" wheel bubbles the tires, so I don't think I getting full traction..

Would I be better off with a tire like a 225/70 (7" width) or 235/70 (8" width)?

Wouldn't I get a faster turn in response with the narrow tire being it is more square on the 7" wheel?

Thank you,
Jeff
 

·
Registered
Joined
·
6,182 Posts
All of the Tire Tread Width is on the road
the Side Wall of the Tire is always wider than the Tread Width
and yes the smaller the Width of the Wheel the more Bulge the Tire will be

The more Tire on the ground the better the car will ride / handling IMHO on the street
and that is why some Wheel Widths are not recommended for the Street
eg. JEGS Sport Star Cast Aluminum Wheels | JEGS

Road Course guys run the widest Tire/Wheel combos possible
based on their cars suspension / room in the Fenderwells etc.
so that they can make the car turn better in the corners

A smaller width Wheel/Tire might give you a better/quicker response at first
but as the car starts to turn the forces/pressure on them, when they have less Tread Width on the ground/pavement,
could/would result in loss of front turning ability

For Rear traction the more Tire on the ground/road and the Wider the Wheel Width the better

My cars Fronts - Wheels = 15"x 7" BS 3.50”
"""""""""""""""""- Rubber = P205/75R15 – Tread Width 6.25” /Side Walls Width 8"/ Dia 27.1"
"""""""" REARS - Wheel = 15"x 8" BS 4.25”
"""""""""""""""" - Rubber = M/T Sportsman S/R Radial 28''x 12''R x 15''LT Tread Width 10.4"/ SWW 12.1"/Dia 28"

This is based on the room I have in my car's Fenderwells at this time

In the future after some changes to the exhaust pipes at the back of the car
I will be putting 10" Wide Wheels in the Rear Fenderwells of the car
and also 8" Wide Wheels for the Front of the car for the Street Driving I do
this will provide a better Ride / Handling / Traction for the car . IMHO
 

·
Registered
Joined
·
3,697 Posts
Discussion Starter · #5 ·
I like the 245/60 all the way around.. Thanks for the link.. I forgot about Mickey Thompsons, I think they are made by Cooper...
 

·
Registered
Joined
·
1,148 Posts
I've been following this thread as I need new tires. Currently have BFG 275/60-15 rear & 235/60-15 front. I am concerning getting Cooper tires as replacements. USA made (I think) about $40 cheaper then BFG. They get very similar reviews on Discount Tire web site. Anybody using them?
 

·
Premium Member
Joined
·
4,966 Posts
Ditto on the Coopers, excellent tire!
 

·
Premium Member
Joined
·
17,566 Posts
I have Cooper tires on all 7 of my vehicles. I think they are a quality tire at a reasonable price.
I think Cooper, MasterCraft and M/T are all made by Cooper...


Hydro462 said:
The 7" wheel bubbles the tires, so I don't think I getting full traction..

Would I be better off with a tire like a 225/70 (7" width) or 235/70 (8" width)?
Sidewall "bulging" or bubbling does NOT necessarily mean you aren't getting the full tread width on the ground... Different lines and brands are going to react differently. IMO, anything within the manufacturers recommendations for wheel width should work fine. Figure that the rubber is pliable to a point, so unless you go well outside of wheel width recommendations, you are probably not going to make a noticeable difference in handling... Imagine if people were getting uneven wear from tread-on-the-ground variations when still within the manufacturers specs and recommendations. Companies wouldn't want that attention or liability.


IMO, you will have better handling and traction with the 255 on a 7"rim than with a 225 on a 7 inch rim or a 235 on a 8 inch rim... Not only for more tread on the ground, but also for a slightly shorter sidewall...

IMO, rubber compounds and tire construction are going to affect handling more than a slight variation in wheel width, etc... OP mentions he wants the best handling, but with a 15 inch wheel. Not sure whats available, but IMO Cooper/M/T, BFGs, etc are NOT going to be the best tires for handing... Decent compromise maybe for a street car...

I used to run 265/50-15 on 15X7 rims on the front of my '66, tread was flat on the ground (based on some burnouts with these wheels/tires combo on the rear)... I was going to run 245s, but 265s fit...Handled well, but I never really quantified it... BFGoodrich Radial T/As anyway, so not the best rubber compound for traction...


BFG Radial T/A and Cooper Cobra GT's have similar sizing specs.
for the 255/60/15, recommended rim widths are 7"-9", with 10.2" section width measured on a 7.5" rim...

for the 225/70/15, recommended rim widths are 6"-7.5", with 9" section width measured on a 6.5" rim...

for the 235/70/15, recommended rim widths are 6"-8", with 9.5" section width measured on a 7" rim...

BFG notes a tire wear rating of 400, while Cooper lists 440, both with a traction rating of "A"... For whatever its worth...
 

·
Premium Member
Joined
·
7,046 Posts
Racers have known for decades that running wider rims than tire width increase roll stiffness and break loose more progressively under side loading. The rounded profile of a rim that is as wide as the tire or slightly narrower makes for a quicker reacting car due to the increased roll stiffness.

The shape of a tire's contact patch or "footprint" greatly influences its performance and is dependent on its profile or "aspect ratio". Low profile tires (most performance tires) have a short and wide contact patch that is effective in converting the driver's input into very responsive handling, cornering stability and traction.

On a 7" rim a max of 235mm cross section or preferably a 225 or even 215 is recommended. The secondary consideration is the aspect ratio where you would want to use the shortest tire you could find.

I've posted this chart before. http://www.chevelles.com/forums/attachment.php?attachmentid=409753&d=1482779707
When using the chart, instead of minimizing your rim to justify putting too wide of a tire, think in terms of maximizing your rim for best fit.
 

Attachments

  • Like
Reactions: hydro462

·
Registered
Joined
·
1,148 Posts
Well I got a set of Cooper cobras on my 67. Had a bad tire pull, 1st front tire replaced. Had a bad vibration at 65 mph, went back to Discount tire & they did a free road force tire ballance, had to dismount & reposition all 4 tires before ballance. Found one bad front tire, replaced it & road force ballance. They said they got that one as good as they could & ordered a new tire for the front. That would be the fourth tire. Talked to my advisor there & we decided to order a set of BFG's for the car. With there sale it's only $120 more for them. We will see next week when they come in.
 

·
Registered
Joined
·
6,916 Posts
That sucks about the Coopers. It makes me wonder if your wheels are out of round. The tires might be so hard to balance since its constantly fighting with an our of round rim. Though you did say a bad pull, which would suggest bad tire since bad balance would typically give vibrations.

I'd cancel the BFG's and get some M/T Sportsman ST's.
 

·
Registered
Joined
·
1,148 Posts
Mickeys are made by Cooper. They did say one wheel was a little off, but there was no vibration with the old BFG's. Got to get good tires on it as a friend & I are planning a trip to the March meet at Famoso drag strip near Bakersfield Ca. Old funny cars & front engine dragsters, should be fun, hope it stops raining!
 

·
Registered
Joined
·
6,182 Posts
Gary did you check to see if the Wheel was the problem ?

Before I mount new Tires on any Wheel new or used I have the Shop check the Balance of the Wheel
if one or all are off too much then I do not put the Tire on them

no use of putting a good Tire on a bad Wheel
I do this to all my Tires / Wheels for my street and track
 

·
Registered
Joined
·
1,148 Posts
Got the BFG's mounted yesterday. Much better than the coopers. The RF that we had problem with ballanced out with 1/2 oz. The tech that did the road force ballance showed me the wheel has heavy spots but can be ballanced with a good tire. Some of the Coopers had up to 12oz on them. The wheel is not bent or out of round.
 
1 - 17 of 17 Posts
Top