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1993 Buick Roadmaster Estate Wagon
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While shopping for tires for my car, I couldn't find any writeup of these tires on a GM B-body, so I figured I'd put one together to help anyone who considers these in the future.

When I bought my '93 Roadmaster wagon last Fall, the alignment was WAY off. Consequently, the front tires were pretty much finished while the rears were fine. Due to lack of funds at the time, I settled for buying a new pair rather than a full set. So I've been running mildly-worn General Altimax in front, and brand new Crugen HT51's out back, both in 235/70R15 on factory original aluminum 15x7 wheels. They've been decent and comfortable, but nothing to brag about. Especially with the rear swaybar I installed recently, the limits of those tires were more obvious than ever.

For this year, I decided to put on something a little more "spirited", and experiment a bit with size. I wanted to keep the OEM 15" wheels. Based on other posts on this forum, I figured 255 or 275 tires should fit, so that's mostly what I looked at.

I kept coming back to the Cooper Cobra Radial G/T, but like everything else in these sizes for 15" wheels, it's only got a speed rating of T. I don't necessarily plan to drive at 120+mph for extended periods of time, but in my experience, tires with a lower speed rating tend to have super flexy sidewalls. I really wanted something with a speed rating of H or V. I've run Cooper Cobra G/Ts on other cars in the past ('78 Trans Am, '71 Datsun Z), and came away unimpressed. They're very much an "older" style of tire.

Enter the Vitour Galaxy R1. I don't know if Vitour has a common parent company. It looks like they're a South African company, though I'm not even sure about that. They're made in China according to the TIN code on the tire. These tires are available in most of the sizes that the Cooper Cobras are (so, a lot of classic car sizes), except they have a much more modern tread pattern that's intended to be performance-oriented. They also have a speed rating of H or V, which is much higher than the S or H that's prevalent in these sizes. Their price is downright reasonable, too.

My next dilemma was to choose sizes. I disabled ABS on this car, so a staggered setup is a possibility (255/60R15 front, 275/60R15 rear). Or I could stick to the OEM size (235/70R15). Or I could balloon-up all around (255/70R15). I ended up going with the latter option. My logic is that I like the bump-smoothing of taller sidewalls and greater air volume at lower pressure. If it compromised handling too much, well... they have a wear rating of 400, so it's not like they'll last all that long anyways 🤣 (for comparison, Cooper Cobras have a wear rating of 440) If I want something more aggressive next time, maybe I'll try the staggered setup. Everything's a compromise anyways...

I received the tires a couple months ago from Performance Plus Tire and they've been sitting in my garage ever since. They're gorgeous. The tread pattern looks really modern, the compound is grippy, and the white letters look real nice. I dunno how long they'll stay white, it's just a thin coat of paint on the molded rubber, but I can always re-apply it if it wears off prematurely. I don't get why they say M+S on them... they'd make a real lousy snow or mud tire. I wouldn't run these on anything but pavement and never below 42f.
198426


Incidentally, that's a heck of a joint seam in the tread. I typically only see that in cheap budget tires from WalMart. But once the flash has worn off, it should be barely visible anymore.

In 255/70R15 size, these tires have a load rating of 108. That means I can air them way down compared to the OEM 102-rated tires and still have the same load carrying capacity. That makes for a nice, cushy ride while maintaining their round shape. I've been running the OEM-sized tires at 32psi, which I settled on after checking contact patch with my tire pyrometer (I do this for even tire wear, not for max performance). With these larger tires, I decided to start at 27psi, and I'll adjust that once my friend returns the tire pyrometer he borrowed...😤
198427


They balanced out decently. Two of them needed a 2oz weight on each side, the other two needed less than 1oz on each side. This could be due to the wheels as much as the tires, they're dirty and battered. They all zeroed out in one try on a recently-calibrated balancer with a 1/8oz tolerance. I may spend time cleaning them up and matching high-low spots in the future or I may not, depending on how they end up feeling long-term.

First drive impressions:

These tires are mighty grippy! Night and day difference from the old General Altimax fronts I had on there. The Crugen HT51 rears I was running may have been a little closer in grip, but they never served steering duty so it's hard to know for sure. Obviously the 255 width and larger diameter means it's harder to smoke the back tires than it used to be, but this is just a tired L05 trying to turn them. In the curves, this tire is confident and grippy, and traction lets go very gradually at the limit. Taking corners aggressively no longer results in embarrassing tire squeal (unless I WANT tire squeal).

Steering response is decent, slightly worse than the previous General Altimax. This could be because of the taller sidewall, the lower pressure, or the fact that these tires are still brand new and the compound needs to firm up some more. So steering input isn't as rewarding, but the increased grip is still very evident. I'll revisit this in a few hundred miles and after I've had a chance to fine-tune the pressure.

These tires are SMOOOOOTH... they soak up the bumps better than the Generals and Crugens ever did. Spring thaw is happening in Vermont right now, and the roads are awful from a Winter's worth of beating by the plows and frequent frost heaving. This is especially bad near the outside edges of the road, where the pavement sinks faster where the ground thaws first. I was purposely driving on this ragged edge, and it barely shook the car at all. Just kind of a gentle rumble.

At 75mph on the highway, they're ultra smooth and whisper quiet. I felt no weird balancing issues in the steering wheel. No vibrations anywhere in the car. I tried with all windows down then up, and I can barely hear them. Just a very faint whisper, no hum or growl. Over bridge expansion joints, they're virtually silent.

I recently installed new brakes up front (HD12 rotors from NavyLifer on Kore hubs, J55 calipers and Hawk Super Duty truck brake pads with stainless steel braided lines), and these tires are a perfect match. For panic stops, the tires provide just enough grip to barely allow the brakes to lock up on dry pavement, with good modulation control. Basically the tires allow me to get the most out of the brakes. I'll write up a separate post about those brakes.

So far I've come across a couple of drawbacks; First, the bigger tires rub a bit up front at full steering lock. Beyond that, the fit is perfect, and I was able to confirm that there is in fact room for 275 tires on OEM wheels out back if I ever decide to go that route in the future. Second, the torque converter has a hard time staying in lockup when cruising at 75mph on anything but perfectly level road. Again, the weak L05 has more to do with that than anything else. At least my speedometer is more accurate now, it's been showing about 3.5 mph fast at 75mph since I bought the car. Now it's barely fast at all. I'm guessing this will end up hurting fuel economy a bit. I bet the diameter of these tires really shines when I get around to putting in the 6.5TD/4L80E someday, they should be a great match.

So was this a good purchase? My goals were:
  • better grip
  • comfortable ride
  • more modern tread design
  • keep OEM 15" wheels

I've achieved all those goals and more, with a couple of drawbacks. The steering response might improve on its own, or with some pressure tuning, and the struggling torque converter lockup (which is a super minor issue) will totally disappear once I get a more powerful engine in there. The tire rubbing at full lock is such a minor thing, I don't even consider it a real issue. All of this for a grand total of $481 (plus $50 for mounting/balancing). Compare that to $572 for a set of Cooper Cobra G/Ts. In my opinion, these Galaxy R1 tires are superior to Cobra G/Ts in every way. So yeah. This was a good purchase. Though depending on how the steering response evolves, I'm seriously considering going with the staggered setup next time for the shorter sidewall and more aggressive appearance.

198428
 

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Always wondered why 255/70R15 was less popular for our cars than 255/60R15.
Think I might be the only person who ever tried 255/65R15 on a wagon before that size became extinct.

From experience:
1. If you corner too aggressively, you might find the rear tires' outer sidewalls being worn smooth by the upper non-arched part of the rear wheel arches
2. Cannot recommend trying to muscle a 255mm-wide tire into the spare wheelhouse.
Nevermind trying to muscle a 255mm-wide tire OUT of the spare wheelhouse.
 

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Discussion Starter #3
Always wondered why 255/70R15 was less popular for our cars than 255/60R15.
Think I might be the only person who ever tried 255/65R15 on a wagon before that size became extinct.
If these tires were available in 255/65R15, I definitely would've gone the staggered route, because that puts the diameter almost exactly the same as 275/60R15, which itself is almost exactly the same as OEM. As it is, I feel that 255/60R15 is a tad too short. It's significantly shorter than stock. It's unfortunate that those 65-series sizes don't exist anymore.

1. If you corner too aggressively, you might find the rear tires' outer sidewalls being worn smooth by the upper non-arched part of the rear wheel arches
I haven't experienced any such rubbing yet, though I'm sure I could induce if I really wanted to 😂 Especially with a rear swaybar in place.

2. Cannot recommend trying to muscle a 255mm-wide tire into the spare wheelhouse.
Nevermind trying to muscle a 255mm-wide tire OUT of the spare wheelhouse.
😂 I wouldn't bother with a 255 for a spare tire. If I keep a spare at all, it'll probably be a 235/75R15, which I have a few of. My usual spare tire is either a tire plug kit, a can of sealant, or AAA, depending on how bad the puncture is. A lot of times, it's so much easier to plug a tire on the spot than to replace the wheel.
 

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If these tires were available in 255/65R15, I definitely would've gone the staggered route, because that puts the diameter almost exactly the same as 275/60R15, which itself is almost exactly the same as OEM. As it is, I feel that 255/60R15 is a tad too short. It's significantly shorter than stock. It's unfortunate that those 65-series sizes don't exist anymore.
Depends on what your definition of OEM is …
OEM tire specs for 91-96 B-cars:
235/75R15 (28.87") OEM Cadillac Fleetwoods with V4P Tow, V4U Limo, B9Q Hearse, or B05 Armour
225/75R15 (28.28") OEM for 91-96 B-wagons
235/70R15 (27.95") OEM for 91-96 B- & D-cars with V92, or 9C1s with LT1
215/75R15 (27.69") OEM for 91-93 9C6 B-sedans (taxis) with LB4 4.3L V6
225/70R15 (27.40") OEM for 94-96 B-sedans with L99 4.3L V8, some 9C1s with LT1, & 1A2s
205/75R15 (27.10") OEM for 91 sedans (GM themselves 'retconned' this spec, however)
255/50R17 (27.03") OEM for 94-96 B-sedans with WX3 or WX8

255/60R15 ≈ 255/50R17 … if short tires do it for you …
If I'm ever lucky enough to own another B- or D-car, it will wear 235/75R15.
All the other tire sizes have inferior tires options to the tire options available for 235/75R15.
I haven't experienced any such rubbing yet, though I'm sure I could induce if I really wanted to 😂 Especially with a rear swaybar in place.
IF it makes you feel any better, it took about 6 months of cornering at idiotic speeds with my wagon to anonymize the sidewalls.
Funny thing is, after that, there was no further damage. Your scuffage may vary.
😂 I wouldn't bother with a 255 for a spare tire. If I keep a spare at all, it'll probably be a 235/75R15, which I have a few of. My usual spare tire is either a tire plug kit, a can of sealant, or AAA, depending on how bad the puncture is. A lot of times, it's so much easier to plug a tire on the spot than to replace the wheel.
Ifyou somehow COULD, it would not be the effort, is my point. I physically could not stuff a 255/65R15 tire in the spare wheelhouse, not for lack of effort, but for lack of success.
Never tried with a 245mm-wide tire …

Nevermind what my next car is, I want one of those inflatable reinforced balloon 'jacks' that off-road enthusiasts use.
 

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Discussion Starter #5
I'm still not sure why my speedometer was so far off with 235/70R15 tires on there. That's what the tag says the car came with. It just hasn't been accurate until now with the much larger 255/70R15 tires on there... seems odd
 

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So far as I know, it's supposed to be illegal for a speedometer to display slower than 'actual', anywhere in the world, so manufacturers tend to err on the side of caution.
Still, yes, that is odd …
 

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Discussion Starter #7
oh it was displaying faster. For a long time, I was the slow-poke on the highway who thought he was going 75 when in fact I was going 71. The new tires have sped up the car to catch up to the speedometer
 

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I got that it displayed faster, as it should. Margin of error is larger than normal, though.
Weirder still is that 255/70R15 happens to fit the speedometer just right …
 

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Nevermind what my next car is, I want one of those inflatable reinforced balloon 'jacks' that off-road enthusiasts use.
Also those 12V electric scissor jacks for like 60 bucks are pretty slick. Seen tow trucks using them.
 

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Also those 12V electric scissor jacks for like 60 bucks are pretty slick. Seen tow trucks using them.
Hoping the following is a silly question:
Do they make one that'll lift a Suburban 2500?
 

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Always thought the footprint of such type jacks was a bit small for my taste.
Still, my lower back thanks you.
Also, still want to find a better value for

Offroaders love 'em, but I think they'll work just fine on badly maintained NYC roads too (although I'd prefer a shape that would be less susceptible to rolling over).
I prefer 235/75R15 & 255/70R15 (and their 16", 17" & 18" equivalents) for the same reason - large contact patches.

With apologies to GoremanX for being a distraction.
 
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