Where to buy oem tires? - Page 3 - Mercedes GLA Forum
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post #21 of 48 Old 06-04-2019, 06:50 PM
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Originally Posted by RichZilla View Post
Does a 9" wheel with a proper offset fit on a GLA45? That's a bunch wider for sure.

I live in Sport+ mode. That's the very first thing that happens once the car is started. I rarely use full manual mode. I'll try it on the track for sure though. Might be a little a little beneficial if used properly.

yes here is the video with 9" rims on gla. looked good, but not sure about off set.
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2015 GLA 45 DESIGNO MOUNTAIN GREY MATTE, 19"OZ ULTRALEGGERA HTL, AMS AIR INTAKE,AMS TITANIUM STRUT BAR, GIRO ROTORS, BRONDEX 200 cel DOWN PIPE, AMR PERFORMANCE STG2

Last edited by caug; 06-04-2019 at 06:53 PM.
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post #22 of 48 Old 06-05-2019, 12:46 PM
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I am looking at Michelin 4S in 255/40/19 but I think our rims are only 7" wide not 8". The Michelin's need a 7.5 " rim minimum supposedly . Does anyone know for sure? I see Discount Tire has the OEM Conti's which have been pretty good.
OEM AMG 19" are 8J x 19 ET43.5 - 5x112 bolt pattern
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post #23 of 48 Old 06-05-2019, 01:11 PM
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OEM AMG 19" are 8J x 19 ET43.5 - 5x112 bolt pattern
Thanks! I think I'll give the Michelin 4S a try!
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post #24 of 48 Old 06-05-2019, 02:00 PM
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Michelin and Continental use different math calculating diameters. To get the MP4S in 20" size we had to use 245/40 ZR20.

Make sure whoever installs your new tires verifies height first!!!
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post #25 of 48 Old 06-05-2019, 04:45 PM Thread Starter
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so an internet tire diameter calculator won't work to compare tire sizes?

Also, the documentation I was looking at stated a 255/40/19 needs an 8.5" wheel, which wouldn't fit. you SURE that michelin fits on a 7.5 and 8"?

Another idea to consider is going smaller. since the 255/40/19 is supposedly 1% smaller diameter than our OEM conti's, it begs the question of considering a 225/45/19. In this tire size there are also several Y and (Y) rated tires. including tires that cost $155 and an highly recommended. They should fit a 19x8 wheel. Of course they are not as wide...

Given that there is no cost benefit to going wider, I'm not convinced it's not just worth it to stay with the contis. The per tire price is the same, and I am not convinced that for 95% of spirited street driving there will be any noticeable difference.

Where I do see the potential for benefit is going down to the 225mm width, where Y rated tires with treadwear of <300 are available for well under $200 per tire. That is a huge savings. Obviously we aren't looking at tires with treadwear 500 (or 310, for that matter).
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post #26 of 48 Old 06-05-2019, 05:01 PM
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Within a brand the math calculations work. But if you change brands have you're installer compare heights. I thought I had the right Michelin tires. The math worked and Tire Rack agreed. My installer compared once he had the tires off and found the problem. Ordered a new size and all was good.

245 is the max width for our standard rims.
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post #27 of 48 Old 06-05-2019, 11:39 PM Thread Starter
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I've been looking more and more at the Falken Azenis tires. Looks like many tesla owners like them, as do a smattering of other sports cars. They are only 225's, but they should fit the OEM wheels unlike the other 19" offerings, and at half price makes it more palatable to replace every 10-12k miles. Assuming the reviews are all true of course.
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post #28 of 48 Old 06-06-2019, 08:57 AM
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Originally Posted by Whiterabbitt View Post
so an internet tire diameter calculator won't work to compare tire sizes?

Also, the documentation I was looking at stated a 255/40/19 needs an 8.5" wheel, which wouldn't fit. you SURE that michelin fits on a 7.5 and 8"?

Another idea to consider is going smaller. since the 255/40/19 is supposedly 1% smaller diameter than our OEM conti's, it begs the question of considering a 225/45/19. In this tire size there are also several Y and (Y) rated tires. including tires that cost $155 and an highly recommended. They should fit a 19x8 wheel. Of course they are not as wide...

Given that there is no cost benefit to going wider, I'm not convinced it's not just worth it to stay with the contis. The per tire price is the same, and I am not convinced that for 95% of spirited street driving there will be any noticeable difference.

Where I do see the potential for benefit is going down to the 225mm width, where Y rated tires with treadwear of <300 are available for well under $200 per tire. That is a huge savings. Obviously we aren't looking at tires with treadwear 500 (or 310, for that matter).
Yes you are correct! It looks like the 255/40/19 Michelins need an 8.5" rim. Darn! Well, I will probably just stay the the OEM tires. Though I like the idea of dropping down to 225. I'll have to research those sizes. Thanks!
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post #29 of 48 Old 06-06-2019, 01:03 PM Thread Starter
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Here's a question for you guys. How do you quantify grip? Not manufacturers who have fancy equipment, I mean every day people, maybe your average SCCA member. The guy who wants to really know if a tire is more grippy than another, do they have any real way to get there besides average track times on track day? Any tool they can use to actually measure one tire vs another?

Everything I read online is just stuff like how they "feel". I can make myself "feel" alot for a tire that is half price! I prefer data. But not sure how to go about generating it.

Any ideas?
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post #30 of 48 Old 06-06-2019, 04:27 PM
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Originally Posted by Whiterabbitt View Post
Here's a question for you guys. How do you quantify grip? Not manufacturers who have fancy equipment, I mean every day people, maybe your average SCCA member. The guy who wants to really know if a tire is more grippy than another, do they have any real way to get there besides average track times on track day? Any tool they can use to actually measure one tire vs another?

Everything I read online is just stuff like how they "feel". I can make myself "feel" alot for a tire that is half price! I prefer data. But not sure how to go about generating it.

Any ideas?
The UTQG rating (Uniform Tire Quality Grading), or "Treadwear Rating" is the closest thing I know of. There are of course other factors in the design of the casing and the tread pattern itself, but the treadwear rating number is pretty dang proportional to the resulting "grip".

There is a TRACTION grade (AA, A, B, C) that directly relates to G-force grip numbers, but the ratings are fairly wide ranging. You can have two "A" grade tires with different UTQG numbers and different resulting grip.

I think there have been some decent tire shootouts in the past, with specific tires going head to head on identical cars. I found those to be somewhat helpful. Not many around though.

For reference, In autocross competitions the lowest UTQG number allowed for a "street" tire is 200, and that's pretty sticky. I've run down to 180, but not recently. Drag slicks are more like 40. Winter tires don't seem to have a rating? (I only looked up a few brands though)

We all know how opinions and buttholes are similar. Everyone has one, and they all stink! If we're talking about performance tires, I don't trust anyone else's opinion unless they've had all the tires tires they're talking about on the track, and have at least some performance driving credentials. If you've never been on a track with full races tires being pushed to the edge, can you really have a proper baseline for other "lesser" tires? It definitely seems helpful to have experienced the extreme ends of the spectrum to know where something else lies in between. I don't put a lot of weight on reviews and opinions, but they can shed light on some things.

In the end, if you don't plan on track days, and don't regularly push your car to the edge on the street, then the stock Conti's are really good tires in my limited opinion. That being said, I am still going to do my best to find a wheel/tire combo for my 2018 GLA45 that will allow me to mount up the RE-71R's! But my perspective is heavily skewed by track time. All the flinging rocks from a UTQG 200 tire would freak out pretty much anyone not used to that. In parking lots, I've had small rocks (the size of a grape?) get tossed up on the hood of the car when turning tight corners going slow. Not cool.

To hesitate is a waste of time.

Last edited by RichZilla; 06-06-2019 at 04:31 PM.
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