17X7 & Speedometer Reading?

[dezquest]

With 17x7 Rims on a 87 244, how much is the Speedometer going to be off by? Just wanting to know before I put 'em on.

[245gti]

It depends far more on what tires you plan to run than wheel size. Run a 215/45/17 and you should be pretty darn close to the original 195/60/15.

[towerymt]

Stock size on an '87 244 is 185/70/14, which is about 24.2-24.3" tall. A 215/40/17 is about 23.9" and a 215/45/17 is about 24.7". A 225/40/17 would be closer at around 24.1", but it's an odd size. Go for 215/45/17.

[mikep]

My favorite one,
http://www.miata.net/garage/tirecalc.html
It shows the apparent change as a larger or smaller circle superimposed on the original tire.

Others of note:
http://www.corral.net/tech/gearcalc.html

http://gs.tolan-hoechst.com/tirecalc.htm

[dezquest]

I am actually going with 205/40/17. Thanks for the info. Especially the tire calc. I will actually be going slower than the speedo which is good. I travel 160 mi. per day & there are a lot of state troopers in Tenn. waiting to give a B.S. speeding ticket!

[towerymt]

I am actually going with 205/40/17.
215/40 would be better just for more sidewall. I've put a few miles on 205/40/17, and they're quite stiff (mine were r-comp racing tires, but still, they're really small sidewalls).

[Smitty]

I see a lot of posts here about running ultra-low profile tires. Pardon me for being on the stodgy old-fart side, but as a long-time Volvophile and a cautious aerospace engineer I feel a need to offer some caveats...

The OEM tire size for the 240 sedans was of course 185/70-14, and most of the posts I see here are concerned with maintaining something close to the same installed tire diameter to minimize speedometer error, which is a good thing. And in general, 205 is the widest tire you can safely run on a 240 without rolling the fender lip. But what I don't see is any regard for the tire's LOAD RATING.

The 185/70-14 has a load rating of "88", which translated means 1235 pounds. Multiply by 4 and you have SAFE tire capability of 4940 pounds, which gives about 50% "margin" for a 3300 pound car if all the car did was roll slowly. But we accelerate, we corner, we brake, all of which impose g-forces on the tires. I doubt any but race-prepped Bricks corner or brake at 1 g, and they sure don't accelerate at 1 g, so a 50% margin is probably adequate.

Now take the 205/40-17 tire size which was being discussed. According to Tire Rack, that size comes in load ratings of 80 or 84, depending on the tire manufacturer. A LR of 80 is 992 pounds, which is a 20% REDUCTION in the tire load capability over the stock size. And it's not grandma buying those tires, it's the performance-minded owner who's going to take advantage of the performance that a sticky, stiff-sidewalled tire offers... and that means higher loads on the tires than presumably a stock tire would ever see.

And there's more to load ratings than just the weight of the car... a load rating is not assigned based on the ability of the tire to remain structurally sound just when the car is parked and loaded up, but when it's running on the road - getting hot, having the sidewall flexed, etc. Decrease the load rating below that which was specified for the car by design engineers who actually do productive stuff in between coffee breaks, and you're compromising safety and tire life.

My Brick is very lightly modified; no turbo, just a mild (VX) cam, and for reasons of economy I run some 15x6 Dracos off a 700 turbo; the 205/60-15 tires have a LR of 90, which is 1325 pounds... about 7% higher than stock. For me this translates into slightly better wear than I should expect from an H-rated tire, and I'm happy about that. Doing a little more searching on Tire Rack, I see the 205/55-16 has a LR of 91 or 1356 pounds, even better... drop down just one step to a 205/50-16 and the LR is back at 87, which at 1201 pounds is just a tick below the OEM tire but that wouldn't cause me any concern.

I offer this as information only, and not with a sense of "tsk-tsk"-ing. I just want fellow Bricksters to be armed with good information so they can make informed choices about the equipment they choose.

Smitty (in the AZ desert)

[245gti]

Good info Smitty. Thanks for that. Something that a lot of people don't consider...

One item that I'll challenge you with though is tire width. It really depends on wheel offset. Because of Volvo's wonderful and relatively exclusive bolt pattern, we are forced to use a fairly small selection of wheels. What a lot of guys have been doing is buying FWD wheels and then correcting backspacing with spacers or adapters. With correct backspacing I had 245/45/16 tires inside the rear wheel wells of a 245 and while they rubbed at times, it wasn't substantial. With correct placement, one should be able to run a 225 and possibly even a 235 tire with no need to roll the fenders... I'm not sure on a 7 or 9 series car but those tires and wheels are now in the hands of a 740 owner and we'll see soon enough how they fit...

I currently run 205/55/15 tires on Virgo wheels and they're nowhere near rubbing...

[Smitty]

gti, you're absolutely correct re offset; thanks for the correction. My statement about 205 being max section width was based on no mods; adjusting the offset via combinations of FWD wheels and spacers was not on my mind. With an 850 and its nice 15 x 6.5 wheels in the family, the thought of spacers was attractive but the cost was always daunting.

205's with any RWD Volvo wheel should not give any interference problems except MAYBE on an extremely lowered car.

Smitty

[towerymt]

I don't know what problems are likely to occur from running a significantly undersized tire on a 240 that's driven harder than originally intended. But I've had no such problems doing exactly that, so I'll probably continue to do so. The tirerack.com tiretech gives only the obvious answers, to paraphrase: "If the number is lower, load rating is decreased...if the number is higher, the load rating is increased"

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35

So far on my 244 I've used (and driven very hard):

205/40/17 = 80 (992)
195/50/15 = 82 (1047)
195/60/14 = 85 (1135)
205/50/15 = 86 (1168)

185/70/14 = 88 (1235)

And I even drifted on a pair of 175/60/14 off brand tires for an entire afternoon (practice event with lots of runs). Tirerack doesn't even sell anything in that size, but I'm guessing the load rating is quite low.

I'd be more concerned about bending a wheel with 205/40/17 tires than I would worry about load rating personally. But it's something to consider. A smaller tire is going to heat up faster and wear faster than a larger tire.

[mikep]

Load rating engineers take into account cornering, potholes, etc. So as long as your 500# corner is rolling 500#+ rubber, it's a good thing.
I teach this sort of thing all the time, and usually it is only ignored by the guys who want to put 175-50-13 rubber on the front of their V6 S-10s riding around on the bumpstops.

Oh, and welcome to the forums, Smitty.
I taught a few guys from NASA Wallops that ended up out your way. (night classes at community college) Mostly balloon and rocket engineers, but one ended up at Skunkworks for a while.

[DaytonAE86]

http://www.miata.net/garage/tirecalc.html

[dezquest]

Thanks again for all of the help guys. I just got the tires & rims delivered to my house a few mins ago. I am actually got spacers on the way that I am getting from Dale ( 245gti ). This is also a N/A Daily Driver 240, so no racing plans for it. Just upgrading to an A-cam, e-fan, and moding the air box. Also Yokohama AVID H4S 205/40R17 84H All-season Ultra High Performance tires are rated to last at least 60,000 mi. (of course proper rotation and balance) I have considered lowering the car it slighly like 1" or something, and thats maybe, so I think I will be alright.

[towerymt]

I have considered lowering the car it slighly like 1" or something, and thats maybe, so I think I will be alright.
It's going to look kind of funny with short tires and no lowering...

[dezquest]

How far do should I lower it safely with GT swaybars? I plan on Making a bodykit out of V70 bumpers and GT Styling Sideskirts @ the beginning of August. I thought that would make up for some of height off the ground.

[mikep]

http://www.miata.net/garage/tirecalc.html
repost

[towerymt]

repost
grow up. I already resisted that temptation. :-P

[mikep]

grow up. I already resisted that temptation. :-P
no, YOU grow up.

[towerymt]

no, YOU grow up.
no, you

[klr142]

If you drive 160 miles a day, you should've gone with a tire that's taller than stock rather than shorter than stock, IMO, especially if you're not going to lower the car... 205/40s are going to look mucho funny, and the reason I say go larger than stock rather than smaller, GAS MILEAGE.

I like this calculator more than the Miata one: http://gs.tolan-hoechst.com/tirecalc.htm

With your 205/40s, your car is going to think it's going 165 miles each day, instead of something like 157 with 215/45s. Currently I'm running 235/45s...

What made you decide on 205/40s so fast anyway?

[945ti]

If you drive 160 miles a day, you should've gone with a tire that's taller than stock rather than shorter than stock, IMO, especially if you're not going to lower the car... 205/40s are going to look mucho funny, and the reason I say go larger than stock rather than smaller, GAS MILEAGE.

Depends on the type of commute. You are actually likely to get better economy on a shorter, lighter tire if you are slowing down and accelerating at lower speeds regularly. Only on pretty constant load highway driving could I really see an advantage. Even then, it might be minimal/non-existant in my case driving any of the volvos, as they all have really pretty tall gears (3.54/3.31) already.
I'd rather make the diffy taller to improve economy and reduce rotating and usprung weight by running smallish lightish tires on lightish/cheapish rims as some sort of compromise between econ and go fast.

[Tom Wiley]

I have 205-55-16 tires and i would like to a-know if i a-lowered (one inch with TME springs from IPD) my car would I a-be a a-rubbin? (245)

[klr142]

Depends on the type of commute. You are actually likely to get better economy on a shorter, lighter tire if you are slowing down and accelerating at lower speeds regularly. Only on pretty constant load highway driving could I really see an advantage. Even then, it might be minimal/non-existant in my case driving any of the volvos, as they all have really pretty tall gears (3.54/3.31) already.
I'd rather make the diffy taller to improve economy and reduce rotating and usprung weight by running smallish lightish tires on lightish/cheapish rims as some sort of compromise between econ and go fast.
That's what I'd thought, but that's not necessarily what I've found... During your commute in these stop and go situations, you're not going to be giving it all the gas you can, and your wheel/tire weight is not really going to come into play I'd think. All I know, is that I have better gas mileage all around... ;)

I'd rather run lighter wheels/tires any day of the week(and different gearing, if I wanted), but I'd probably not go smaller than the stock setup unless I was playing on the track. I'd rather not go taller, heavier wheels/tires like I have, but that's what was made available to me.

I have 205-55-16 tires and i would like to a-know if i a-lowered (one inch with TME springs from IPD) my car would I a-be a a-rubbin? (245)
You should have no rubbage.

[DaButcher]

As stated above, it's really about the tiresize.


I used to run 225/45-ZR17W, but now I run 225/35-ZR18Y.

The 225/45-17 was 0.5% offset, but I think I now have approx. 3% offset.

In Norway, we are allowed to have 5% offset in either direction (+-).

EDIT:
Regarding rubbing: This is VERY dependant on the ET (offset) of the rims, centric to the hub.
You also have to fix the fender lip, as that is very poor designed on the 200 series.

[mikep]

I like this calculator more than the Miata one: http://gs.tolan-hoechst.com/tirecalc.htm


That's why I included it in my group of calculators (in my first post), each has its uses. I like the miata.net calculator for show and tell, but the tolan-hoechst calculator does more.

[dezquest]

Yeah that Calculator def. came in handy. I actually bookmarked it. My commute to work everyday is all highway. I live right beside the interstate. I go 80 miles each way. Looking get lowering springs soon. I got the tires mounted and balanced this weekend, and put them next to the wheel and they didn't look that much smaller, but we'll see once I get the spacers in the mail. Right now working on e-fan conversion, and need to replace Head gasket before I put it back on the highway.

Thanks for all of the input.

[klr142]

That's why I included it in my group of calculators (in my first post), each has its uses. I like the miata.net calculator for show and tell, but the tolan-hoechst calculator does more.
Doh! I missed it.

[dezquest]

Okay so this weekend I put on Turbo swaybars, bushings, Brakes, Drilled rotors, Spacers, and the 17x7 ADR wheels. I found out something interesting. Seems that the owner before me put on the wrong size tires too. My wheels were about 1.5 inches larger than the tries that were on the Corona. Even the Spare tire was a little larger. So go figure... Anyway I put the wheels on and they made the car look 10x better. I am very happy. I gotta get some pics posted, but not until after I finish fine tuning the A cam that I dropped in over the weekend. I did decide to lower it (Lowering springs on the way), but it actually looked fine as it was. Got new shocks and struts too, but that'll be a later project. Thanks for all the help.

[mikep]

Very cool.