10 replies to this topic

[sigmfsk]

I'm looking for Z rated tires that would look as close as possible to stock on a bluesmobile.

Due to limited 15" Z rated tire selection, I may have to go to a 16" rim (if there are plain steel rims available).

According to this thread
http://www.bluesbrotherscentral.com/forum/bluesmobiles/9206-thoughts-tire-type-brand.html

the original 1974 Monaco tire size was GR70X15, and the closest size as used today is 225/70/15.

> The new tire is almost identical in O.D. but has a slightly wider O.W. than the 'G' (+ 0.3").
> There was a performance tire option listed in the police literature, in 1974,
> for 235/70/15 tires.
> These are slightly shorter and wider.
> That option required the use of the wider 7.5 inch wheels.

And there seemed to be the consensus that 225/70/15 looked a little small, and 235/75/15 looked great (with 235/70/15 presumably in the middle).

According to this calculator
Car / SUV / Van / Light Truck Tire Calculations
these are the diameters of each of these 15" tires:
225/70/15 27.402"
235/70/15 27.953"
235/75/15 28.878"

I can find the following Z rated tires:
225/65ZR15 26.516"
235/60ZR15 26.102

But they're just too puny.

The following is an almost acceptable diameter, but may be too wide:
255/60ZR15 27.047"

If I go to 16" rims, I can find the following Z rated tires:
235/60ZR16 27.102"
255/60ZR16 28.047"

The last option is about the same circumference as a 235/70/15 tire, and has just .355 inches less vertical distance of rubber as a 225/70/15 (27.402 - 15 - (28.047 - 16)). So it shouldn't look too much like the 20" gold spoke rims on that convertible Monaco for sale.

Thoughts?
What's the widest rim/tire that will fit in all four wheel wells?
Any 16" rims that look like the standard plain OEM steel wheels?
Did I miss any Z rated 235/75ZR15 tires?

thanks,
arthur

For my notes, the Monaco is 5x114.3 bolt pattern:
Dodge - Vehicle Bolt Pattern Reference
which is the same as 5x4.5
Is a 5x114.3 bolt pattern the same as a 5x4.5? - Yahoo! Answers

[scatpack01]

Mopar Action did an article on suspension upgrades and one of the thing they included was a bigger tire and rim. They say a 17x9 or even a 17x10. they didny give a tire size I don't think. I'll have to see if I still have that issue with me.. well here is the link to the article. no tire size but you can estimate what will work.
http://www.bluesbrotherscentral.com/forum/bluesmobiles/8260-make-your-bluesmobile-handle.html

[scatpack01]

reading that article again they had their BM running a 14.80 in the 1/4 mile. That is fast for a humungous car.

[sigmfsk]

Thanks scatpack. I just now requested that backissue (and some others) from Mopar Action.

I also thought it interesting in the link you sent the article from June 2000, where it says:

Besides the aforementioned good stuff, the algoma car is also good for cop sway bars and a set of 6.5 x 15 cop wheels. Harold "the nicest guy in tires" Petterson, is happy to mount all kinds of tires on those rims until they find the biggest ones that would still clear the frame and fenders okay. Hiram schreeches out witha set of Goodyear P255-60-15s in place, raised-white-letters mounted to the inside for the appropriate cop look.

I attach a copy of the pic of the car with those tires from that thread. From what I can tell, it looks pretty good. I think I'd prefer this look instead of 17" wheels.

It looks like 255/60R15s can be mounted on rim widths from 6.5" to 10" (by checking the rim width range under the specs tab on a tire that size at Tire Rack - Your performance experts for tires and wheels), but the Measuring Rim Width is listed as 7.5"

(from tirerack)
The measuring rim width is the industry standardized rim width upon which the tire must be mounted in order to confirm it meets its dimensional targets. Because the width of the rim will influence the width of the tire, a standard rim width for every tire size is assigned and must be used. This standardized measuring rim width allows all of the tires produced around the world to meet the same dimensional standards and therefore, be equivalent with regards to their physical size. The measuring rim width is sometimes referred to as the tire's "design rim width".

So I'm thinking the optional 7.5" width wheels, 255/60ZR15s. What a pleasantly simple solution!

Attached Files

•  tire-255-60-15.JPG   65.2K   6 downloads

[sigmfsk]

Thanks scatpack. I responded to this post on Sunday, but it still hasn't shown up yet. Sometimes it says something like "please wait for moderator approval" or such, and other times a post shows up immediately. I'm still figuring out how the board works.

I ordered the recent Mopar Action issue you reference here:
http://www.bluesbrotherscentral.com/forum/bluesmobiles/8260-make-your-bluesmobile-handle.html
but I think I was most interested in the June 2000 issue referenced in that thread. The guy mounted 255/60/15 on the standard 6.5" wide Monaco rims.

I see on tirerack.com on the specs tab of a tire of that size that a 6.5" rim is the narrowest for that tire. A 7.5" rim is the "standard" width for that tire:

(from tirerack)
The measuring rim width is the industry standardized rim width upon which the tire must be mounted in order to confirm it meets its dimensional targets. Because the width of the rim will influence the width of the tire, a standard rim width for every tire size is assigned and must be used. This standardized measuring rim width allows all of the tires produced around the world to meet the same dimensional standards and therefore, be equivalent with regards to their physical size. The measuring rim width is sometimes referred to as the tire's "design rim width".

So with a 255/60/15 tire, I'd probably get better handling with a 7.5" rim over a 6.5" rim, but if I wanted the best handling, I shouldn't pick a 15" tire to begin with. A 255/60/15 tire on a 6.5" rim will have a larger diameter than on a 7.5" rim. The tires as presented in the article look pretty good.

thanks,
arthur

Attached Files

•  tire-255-60-15.JPG   65.2K   12 downloads

[Monaco74]

I too, have had problems finding a speed rated tire in the correct size. It may mean going to a larger wheel. Stockton Wheel Co. makes 16X8 mopar oem style wheels (like the stock steel ones on Bluesmobiles) using the stock center, so if desired, a 15" dogdish hubcap will still fit. They even make 17" steel wheels with the stock center, but I think that might start looking strange.

[sigmfsk]

> I too, have had problems finding a speed rated tire in the correct size.

Wow; I was just looking again last night for tires; what timing!

Using these baseline diameters:
225/70/15 27.402" tolerable
235/70/15 27.953" good
235/75/15 28.878" great

The closest 15" Z-rated I could find was
225/60/15 25.63"
BFGoodrich Comp T/A
Yokohama DNA DB ES500
Vredestein Sportrac
Toyo RoadPro R610
and others

The closest 16" Z-rated I could find was
235/60/16 27.102"
Falken FK-452
Falken Ziex ZE-912

The closest 17" Z-rated I could find was
235/65/17 29.028"
255/60/17 29.047"
in Yokohama ADVAN S.T.

17" tires would be an exact diameter, but I agree that a 17" wheel might look a little strange. I think 17" are probably out because:

1) they might look a little strange.
2) I think the bluesmobile had "mopar oem 40 series" wheels, as shown on Stockton's web-site here:
Mopar Wheels - Stockton Wheel
and they are only advertised in 16", not 17".
3) They may be ruled out for high speed racing. Ecta-lsr has special rules for large diameters wheels. I think its for wheels > 17", but maybe its >= 17". I posted about this here:
Z-rated 15 inch - Third Generation F-Body Message Boards

I haven't called stockton or ecta, because I think the "looks a little strange" would rule them out anyway.
Interestingly, ecta doesn't require z-rated tires for z-rated speeds (presumably because one is only racing one-mile and there's not enough time for heat buildup). Per the rules
ECTA Rules
> Up to 175 MPH: HR rated tires.

but the Texas Mile
TEXAS MILE // OFFICIAL SITE // 3 DAYS, 1 MILE: NO SPEED LIMIT
does require z-rated tires for z-rated speeds.

I'm thinking the cheapest and arguably best solution is simply to use 235/75/15 for regular driving, and when doing land speed events, just using 15" tires that are small diameter and look dorky. I'll be going too fast for people to see what the tires look like.

So I'm still thinking, and appreciate the thoughts in your post.

your friend in tire planning,
arthur

[Monaco74]

Arthur, there is one solution, but you have to be willing to pay for it. Goodyear makes the Goodyear Eagle RSA 235/70/VR15 (which is a police spec tire). That comes out to just a hair under a 28" diameter. The 235/70/15 tire was an option for the 74 Monacos under the police package (like SIGMFSK said). Did you notice the "V" in the description? That baby is good to 149mph. I doubt anyone wants to break the "Buck-Fifty" mark in a 36 year old sedan that weighs 5,000lbs though.

A little while ago, I also saw the Firestone Firehawk PV41 (Pursuit Vehicle) tire in the same size 235/70/VR that is also good to 149mph.

Goodyear's Go Fast Tire for Bluesmobile's:

Goodyear Eagle RS-A

[scatpack01]

wasn't the factory size more like a 225/70r15? or was it 235/70?

[sigmfsk]

scatpack01 said:

wasn't the factory size more like a 225/70r15? or was it 235/70?

Hi scatpack:

This post
http://www.bluesbrotherscentral.com/forum/bluesmobiles/9206-thoughts-tire-type-brand.html#post104243
has the info

> The P225/70R15 is the current equivalent size tire to the old GR70X15
> (it is as close as possible to matching the old Alpha sizing system, used in 1974)
> ...
> There was a performance tire option listed in the police literature, in 1974,
> for 235/70/15 tires.

My thoughts for using 235/75/15 were different posts in the same thread; one of them has two pics to compare 225 and 235.


I did find the perfect size diameter z-rated 16" tire today:

The Avon Turbospeed CR27, 255/60R16, W Rated.
Turbospeed CR27 | Avon Tyres

> The perfect complement to the luxury and comfort of Rolls Royce and Bentley.

Of course, I can't find anybody that actually sells it. I did find this place:
http://www.tyresite.com/tyres.asp?width=255&profile=65&size=15
that sells 255/65/15 Avon tires - for $500 each! I guess tires for Bentley's aren't cheap.

your friend in cool tires, but not for $2000 plus new rims,
arthur

[sigmfsk]

So the minimum goal is:

A DOT Y-rated tire and wheel that will fit on a Monaco that will meet the requirements of driving 186mph at
-Texas Mile
TEXAS MILE // OFFICIAL SITE // 3 DAYS, 1 MILE: NO SPEED LIMIT
-Maxton Mile
Welcome to ECTA
-Silver State Classic
Homepage Main Menu: Flat Out On A Public Highway! (home.htm)

Other goals:
Fit on a stock 15" wheel.
If not that, fit on a wider 15" wheel.
If not that, fit on any wheel of any diameter that the Monaco will take.

According to the Silver State Classic guys, a 1974 Dodge Monaco that originally came with a 440 was spec'd for H rated tires. And this does seem to correlate with the information in the owner's manual (about the wider 6.5" rims having H rated tires). So despite the fact that my B pillar has a sticker showing a minimum of G tires (load range B), I need to meet the load rating of H rated tires (load range B).

The Police Pursuit radials that were on the car when I got it are H rated tires, with a max load rating of 1770 lbs (pics 1 and 2). The Tire & Rim Association's current yearbook doesn't show the old-school load ratings, but the books from the '80s do. pic 3 shows that a H rated tire, load range B, has a max load of 1770 lbs.

So I must have a tire that has a load rating (at speed) of 1770 lbs. It turns out that at 186 mph, the load rating of a tire is only 85% of its max load rating.

This page shows the reduction for Michelin
Pilot Sport PS2 | Michelin Tires

Here's the reduction for Pirelli
Tyres Load and Load Capacity - PIRELLI TYRE

and for all tires in general
Tire Tech - Air Pressure/Load Adjustment for High Speed Driving Z-Speed

so I need a tire with a max load rating of 1770 lbs / 0.85 = 2083 lbs.

This page
Tire Tech Information - How to Read Speed Rating, Load Index & Service Descriptions
shows that this equates to finding a tire with a load rating of 106, 107, 108, 109, or 110.

Tire rack doesn't allow one to search for tires with a minimum load rating, but this site does:
Discount Tires, Cheap Tire, Michelin Tires, Cooper Tires, Falken Tires
Just do a search for "106Y", for 106 load rated tires at the Y speed range.

The
Pirelli Tires PZero Rosso Asimmetrico 255/55ZR18 109Y
looks like the best choice that I can see. It's the narrowest tire that's Y-speed rated with a load rating of at least 106. And it's the same diameter (29.0") as a 235/75R15 tire (28.9")

There's just no way around it - these tires won't look stock. So if I have these crazy tires just for racing, I might as well not worry about what the wheels look like. The cheapest and safest wheel solution seems to be custom wheels from these guys:
RACING WHEELS, ROCKCRAWLER, OFF ROAD,BEADLOCK WHEELS, THE BEST KEEPS GETTING BETTER BUY MRW
that I learned about from this page:
Construction of my Bonneville Lakester- page 11
that also points out that the wheels
> ...are welded all the way around the attachment between the rim and the center
> section on the inside. That meets the [Bonneville land-speed-racing] rule requirements.

And that also seems to meet the Maxton Mile rule for wheels > 17" diameter:
> wheels must be manufactured for racing purposes or reinforced as follows: By welding
> the entire area of attachment between the rim and the center section...
ECTA Rules

So now I just need to test out a 255mm wide tire up front. If it doesn't fit, then, hmmm...

Attached Files

•  P1010069a.jpg   198.52K   5 downloads
•  P1010071a.jpg   122.93K   5 downloads
•  tirechart.jpg   305.71K   6 downloads