255/50r19 vs 255/45r19

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Hi guys ( and gals ),
Presently doing some homework for replacing the OEM Michelins on my 13 DX.

My brand of preference is General Tires.. I am on my second set of Gen's on my TL [currently on RT43's] and have a set of 17" Gen Ultimax winter for the DX. This is my -go to- brand for tires.. however the OEM size RT43's is not offered... :-(.. but they do have a size that is close... the ratio is 45 instead of 50...

So my question is ..other than the speedo indicating a little faster than reality, is there anything else that would be adversely affected by this small difference in tire size? Is there a -show stopper- detail that I am not seeing?

Thanks for any shared info,
Cheers
J.
 
Originally Posted By: 2K2AcuraTL


So my question is ..other than the speedo indicating a little faster than reality, is there anything else that would be adversely affected by this small difference in tire size? Is there a -show stopper- detail that I am not seeing?

Thanks for any shared info,
Cheers
J.


No
 
Also... If I may add to this little quandary, I can also see some tires that are 245 in the 45 ratio.. rather than the prescribed 255.
Suspecting a slightly narrower tire will still be acceptable??

Or am I pushing thing a little too far now..?
Thanks
J.
 
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1. Wheels spinning faster = more wear-and-tear on everything from your engine to your wheel bearings

2. Anything that depends on wheel speed -- ABS, stability control, AWD torque split if applicable, etc. -- might not operate quite as it should

3. Smaller overall diameter = less rubber on the road, because the contact patch isn't as long front-to-back


Any show-stoppers here? Doubtful. Unless you have to do an emergency stop or swerve, most of the effects will be very slight. There probably won't be any single event, or anything you'd notice in the short term. But a lot of things are affected.

I certainly understand wanting to stick with your go-to brand. I have my own go-tos, and I usually don't want to stray from them. But I'd never buy the wrong size just to get the right brand.
 
The load rating is lower on the 45 profile tire than what's on the door sticker, so perhaps a tire shop may give you grief about it. The MDX is surprisingly porky at 4700lbs and a 98V load/speed rated tire only gives you 3300lbs per axle, so with 5000lbs towing and a decent cargo load you might be running very close to the rated capacity of the tire, plus your camber and toe in the rear will be terrible with a good load on, which heats up the tire more...
If you had the 18" rims then those tires have almost a ton more in load capacity and you have more load room to run smaller tires on those rims.
If you never tow, and never carry a heavy load of people, and you are the only driver, then sure you could get away with it. But especially as the tires age, you could get into trouble with a big load and doing 80mph on tires just above TPMS warning pressure on a hot day...
I actually run slightly undersize tires on my Focus, but it doesn't have the load capacity to get into too much trouble and I run them 4-5psi above the door sticker, but if I sell it, I'd slap a set of the right size tires on it, as the tires I have on it are no longer idiot proof.
 
If my favorite brand of tire did not make the correct size, I would go to another brand that does carry it. And I prefer to stay at 50 series in your case vs 45. Perhaps 55 for a better ride if it fits
 
Originally Posted By: barkingspider
If my favorite brand of tire did not make the correct size, I would go to another brand that does carry it. And I prefer to stay at 50 series in your case vs 45. Perhaps 55 for a better ride if it fits

Reading this reminded me of something I had forgotten: a shorter sidewall means a less compliant ride, more noise, and greater risk of wheel or suspension damage when you hit a pothole.
 
Originally Posted By: IndyIan
The load rating is lower on the 45 profile tire than what's on the door sticker, so perhaps a tire shop may give you grief about it.


OP is also in Ontario, and our laws now state you must not go below the door sticker load rating. Vehicle will fail a safety inspection, and can actually get ticketed on the road.

I second the opinion that if your favourite tire does not come in the right size, find a different tire.
 
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Ah right . thanks for the reminder of the load index... door sticker states 103 and how heat may quickly come into factor.
Towing may be in the picture in the future [ reg utility trailer ] and we can fill this MDX at times with my 2 sons and the back filled with supllies for the week-end trip to the cottage.

here are two proponents I am looking at;
RT43 is - 45 255/45R19 104V SL BSW
and
GMAX 03 - 50 245/50ZR19 105W XL BSW

Pirelli, Conti, Yoko, offer correct sized tires..but the selection for 19" rims bite..!
 
Originally Posted By: 2K2AcuraTL
Ah right . thanks for the reminder of the load index... door sticker states 103 and how heat may quickly come into factor.
Towing may be in the picture in the future [ reg utility trailer ] and we can fill this MDX at times with my 2 sons and the back filled with supllies for the week-end trip to the cottage.

here are two proponents I am looking at;
RT43 is - 45 255/45R19 104V SL BSW
and
GMAX 03 - 50 245/50ZR19 105W XL BSW

Pirelli, Conti, Yoko, offer correct sized tires..but the selection for 19" rims bite..!




I have driven many MDX where the owners have put XL tires on to replace the SL tires. The ride is horrible, it is like driving a dump truck. Although, I am surprised the 105 is considered XL.
 
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Originally Posted By: mightymousetech
Originally Posted By: IndyIan
The load rating is lower on the 45 profile tire than what's on the door sticker, so perhaps a tire shop may give you grief about it.


OP is also in Ontario, and our laws now state you must not go below the door sticker load rating. Vehicle will fail a safety inspection, and can actually get ticketed on the road.


Ah I did not realized that..! luckly the tires I am looking are above the recommended load rating.
 
Originally Posted By: 2K2AcuraTL
Originally Posted By: mightymousetech
Originally Posted By: IndyIan
The load rating is lower on the 45 profile tire than what's on the door sticker, so perhaps a tire shop may give you grief about it.


OP is also in Ontario, and our laws now state you must not go below the door sticker load rating. Vehicle will fail a safety inspection, and can actually get ticketed on the road.


Ah I did not realized that..! luckly the tires I am looking are above the recommended load rating.

XL tires may need to be inflated higher to get the same load rating as SL tires. See page 11
Another one with tables
 
Originally Posted By: LotI
Originally Posted By: 2K2AcuraTL
Originally Posted By: mightymousetech
Originally Posted By: IndyIan
The load rating is lower on the 45 profile tire than what's on the door sticker, so perhaps a tire shop may give you grief about it.


OP is also in Ontario, and our laws now state you must not go below the door sticker load rating. Vehicle will fail a safety inspection, and can actually get ticketed on the road.


Ah I did not realized that..! luckly the tires I am looking are above the recommended load rating.

XL tires may need to be inflated higher to get the same load rating as SL tires. See page 11
Another one with tables


Yeah, I was going to comment on the same thing.

And the tire shop is likely not to want to go there either!
 
Originally Posted By: mightymousetech
Originally Posted By: IndyIan
The load rating is lower on the 45 profile tire than what's on the door sticker, so perhaps a tire shop may give you grief about it.


OP is also in Ontario, and our laws now state you must not go below the door sticker load rating. Vehicle will fail a safety inspection, and can actually get ticketed on the road.

I second the opinion that if your favourite tire does not come in the right size, find a different tire.

The law here states,
A tire fitted on a vehicle shall not,

(a) be of a smaller size than the vehicle manufacturer’s specified minimum size; or
(b) contact any vehicle component so as to affect the safe operation of the vehicle. R.R.O. 1990, Reg. 625, s. 5.

So if you are getting a wider lower profile tires on the same rims, I'm not sure what that means. I bet you are right though, in that the load rating is what inspectors worry about.

We discussed my undersized tires here and it was sort of agreed that a tires durability is a combination of its load rating and speed rating. So going slightly lower in load rating but way up in speed rating is probably getting you a more load resistant tire provided you keep it inflated.
 
Originally Posted By: IndyIan
Originally Posted By: mightymousetech
Originally Posted By: IndyIan
The load rating is lower on the 45 profile tire than what's on the door sticker, so perhaps a tire shop may give you grief about it.


OP is also in Ontario, and our laws now state you must not go below the door sticker load rating. Vehicle will fail a safety inspection, and can actually get ticketed on the road.

I second the opinion that if your favourite tire does not come in the right size, find a different tire.

The law here states,
A tire fitted on a vehicle shall not,

(a) be of a smaller size than the vehicle manufacturer’s specified minimum size; or
(b) contact any vehicle component so as to affect the safe operation of the vehicle. R.R.O. 1990, Reg. 625, s. 5.

So if you are getting a wider lower profile tires on the same rims, I'm not sure what that means. I bet you are right though, in that the load rating is what inspectors worry about.

We discussed my undersized tires here and it was sort of agreed that a tires durability is a combination of its load rating and speed rating. So going slightly lower in load rating but way up in speed rating is probably getting you a more load resistant tire provided you keep it inflated.


That is the old spec. The new Highway Traffic Act came into law June last year. It is easily 10x more strict than the old standard.

http://www.mto.gov.on.ca/english/trucks/pdfs/passenger-light-duty-vehicle-inspection-standard.pdf
 
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Thank you all for your insight and tech details brought to light.

It did really make me re-think my consideration to go for a slightly smaller tire, mainly due to;
as mention above by d00df00d...
2. Anything that depends on wheel speed -- ABS, stability control, AWD torque split if applicable, etc. -- might not operate quite as it should

Although i had overlooked to -load rating- on the potential replacement tire, i was within range..
however mightymousetech comments on the deterioration of ride quality made me think again....

It took a great deal of marital effort to get W to agree and aquire this MDX.. i certainly dont want to compromise any mechanical or ride quality.

And a few day later... The CDNTire flyer came out and the Conti Extreme DW06 are on sale this week .. and these ARE the proper size....even though I had Conti on my 07 Trailblazer.. i was not overly impressed by them..[yes i know.. not the same tire or size] but i found the sidewalls quite mushy .. especially when i was towing our 25' trailer.
things that make you go HMmmmmmmmmmmmmm...

I just might jump on this sale and install next spring...

Anyone have experience on this tire..??

Cheers
J.
 
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The DWS06 is about as good as all-season tires get. If it's the right size, load rating, and speed rating, go for it.
 
Ok So I know you were ALL waiting with baited breath on the outcome of this little tire size enigma...
wink.gif


Well the trigger has been pulled.....

I determined it wasn't worth the trouble of trying to figure more tire options with a deviation from OEM size.

So I went with the Conti Extreme DWS06... reviews were very favorable..



Thanks for your input
J.
 
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