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Just putting the question out there.

Having trouble finding tyres for the GLA's 19" wheels. Have found more options if I go to 245/40 rather than 235/45. There is a 2.28% difference on paper. Would this pose any problems?

Thanks in advance.
 

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With the same size on all four corners, the only problem is the speedometer will be off a little. When speedometer reads 60mph (96.6km/h) actual speed will be 58.6mph (94.3km/h): 2.3% slower.
 

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You never want to go smaller diameter than stock. It will ride like crap and maybe not meet load requirements.

I would stick it out with 235/45-19. 235/50-19 is a little big at 3.7% over.

245/45-19 is good at 1.6% over
 

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Not sure where you are but there are a number of 235/45r19 tires available that work well on the GLA45 (all with trade-offs of course) in both North America and Europe and many more if you go to a 225/50 or 245/45 (about the same turns per mile> around 760 yield a proper speedo reading) plus the higher sidewall choices will give you better ride.

We two 45's, one a 2018 is in Toronto with replacement MO Michelin Pilot Sport 235/45ZR19/XL (99Y) for summer. We also run 215/55' r18's on it in winter. Our 2015 is in Italy and that has recently had Michelin Pilot Sport All Season 4 235/50ZR18/XL 101Y 101Y fitted (we brought the tires from Canada as this tire does not seem to be available in Europe).

The best compromise tire (IMHO) is the new Pilot Sport All Season 4235/50ZR18 as it handles very well, the ride is fantastic and, based on the wear index, it should last a long time.
 

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You never want to go smaller diameter than stock. It will ride like crap and maybe not meet load requirements.

I would stick it out with 235/45-19. 235/50-19 is a little big at 3.7% over.

245/45-19 is good at 1.6% over

You never want to go smaller diameter than stock. It will ride like crap and maybe not meet load requirements.

I would stick it out with 235/45-19. 235/50-19 is a little big at 3.7% over.

245/45-19 is good at 1.6% over
beg to differ. I have that small size Potenza RE71R’s on my 45 and they are awesome.
 

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Yeah, I'm sure they ride great and protect the wheels and suspension better than stock or oversize tires.


In what way are they awesome? Everything we know about physics tells us they will actually work worse in real world driving. Do you think super-stiff sidewalls without any flex are better for day trips that stretch out for 100s of miles on nasty Northeast roads? Sorry, I don't strive for the harshest wheel set-up I could fit on my car, lol, it's already stiff and harsh.

245/50-18 works for me.
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Nobody I ever heard in my life of 25 Audis, 20 VWs, a Porsche and 4 Mercedes EVER said they wanted undersize tires, ALWAYS the biggest they can fit. I feel like I blundered into some kind of logical vortex.

When you hit the pothole, do you want a bigger wheel or smaller one to transverse it? DO you want more or less cushion of the tire? I find this fascinating.

19s are already a mistake to begin with, imo. If someone was stuck with their 19" set, I would want to make it ride better, not worse.

245/45-19 gives almost 1/2" more sidewall than 245/40-19, the improvement in ride will be substantial. Standard 98 load for 245/45, but only a 94 load for the 245/40 ...when OE size 235/45-19 is suggesting a 95 load rating, so I hope you found some XL load tires in that awesome undersize.
 

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26347


Sorry, I wouldn't even put these on my car unless it was specific for the track, even then I would take my $1000 and get the correct size instead.
 

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They way they are awesome is grip. In any kind of driving.

I did not buy a 45 for pothole performance or to drive 100’s of miles in a day. Both are inevitable but I bought the wrong car if I wanted to optimize driving on those.

Also no snow here. Or winter for that matter.

And frankly, for driving in comfort, our seats even leave much to be desired. My wife hates the seats in the 45. Tires are not the only comfort worry!

I shoulda bought an S6 I guess! :)
 

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It really depends on what the original posters local roads, driving conditions are like, and what he bought the car for. In my case I'd agree with Audi Junkie. The reason I went to 245/45/19 is the slightly larger diameter. The car is perhaps .2" taller than stock, and the ride is basically the same. I use mine in Colorado and do like to be able to get around when it snows mildly, so I also went with an ultra high performance all season tire (Continental DWS06 about the best you can get for snow in this category). I also knew if I went smaller, the ride would just be a bit worse, and we do have roads in need of pothole work. In any case, you definitely have more choices in rubber by choosing a 245 width.
 
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Here we go...
wikipedia.org/wiki/Choice-supportive_bias

Choice-supportive bias or post-purchase rationalization is the tendency to retroactively ascribe positive attributes to an option one has selected and/or to demote the forgone options.[1] It is part of cognitive science, and is a distinct cognitive bias that occurs once a decision is made.
That's where I think we are here.

I'll concede that going down a little bit in size might be ok for a vehicle that has some sort of oversize SUV tire already, I dunno....like a Rover, but only on a smooth controlled track condition. You might post a better time on a 60 instead of 65 that happens to be a hair lower w/plenty of cushion to spare. On an already very low profile tire, installed on a mid sized car, no way imo. Even if it was a hair faster on the track (somehow) the trade offs far outweigh any "advantage".

In the wild, nfw are undersize tires better. I could not drive as fast without a cushy tire, our roads simply do not allow it. You would have to slow down or go crashing across rough pavement, even skipping like a stone!

You do realize that a loose set-up that conforms to the road works better in wet, right? A stiff set-up will literally skip like a stone across puddles. I can't believe this even needs explanation.

So, "more grip" is pretty vague. Let's refine it....
More grip if....
You have perfect roads.
You have no rain or snow or even gravel.
You maybe care about track times...?
You think bigger wheels and less tire is aesthetically appealing.
You nor your passengers care one bit about noise, vibration or harshness.
You haven't compared like-for-like tires in S, M and L sizes, so it's just guesswork anyway.
You don't mind bent rims and busted suspension.
You need to save on the purchase price...?
You lack experience with normal premium passenger tires?
You don't mind the low load and wear ratings of this particular tire/size combo.

I listed some nice Nokians that will work better, last longer and half the price. For some reason, they don't suit a narrow racer-boy approach...ok fine, but trying to pawn off BAD advice to general members will be met with increasing mockery. So go read my wiki link and sack-up for a talk with whomever sold you those miserable tires for $1000
 

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Check out this AMG GLC 43, do the tires look tiny or skinny sidewalls to you? It's a 380hp suv, why does it have chunky tires?
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Remember, the GLA is an SUV, not a race car. Funny how close those C43 tires are to mine proportionally...

26354


Would anyone in their right mind take that C43 and reduce the tire height? LOL!
 

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Here's my Metris on jumbo 235/60-17 from OEM 225/65-17. I drive this thing 1000 miles a clip to Daytona in whatever weather throws at me.

26356


What gain, for the love of God, would there be to smaller-than-original tires? There is NONE, it rides like butter.

26355


How about some 215/70-17 to save a few bucks?
 

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ok, now you took me off post.....that blacked out Mercedes van is plenty long, what do you have going on back there? 1000 mile clips, do you have a co-pilot?????
 

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Edit for clarity, it makes total sense that a tire with higher sidewalls or very thin sidewalls will have better small bump compliance. Ditto with having non-performance oriented suspension. It’s just not the application here. It also doesn’t make sense to call the GLA45 an SUV. Does even a single org consider the GLA an SUV besides MB corporate?

Agree totally on the example with the Metris. Again, using a stiff sidewall tire (or any tire selection factor that reduces sidewall stiffness) would probably reduce small bump compliance. Probably important in a Metris!

Can anyone imagine a Metris with 5” of ground clearance, suspension as stiff as the GLA, and rubber-band tires? Ha! How about the GLC? The only SUV seen round here like that are some Model X’s. They do look silly like that, tho cannot comment on drive quality.

It’s all good audi, we won’t have to drive each others cars, whether the roads are wet, dry, rough, or smooth!
 

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Just putting the question out there.

Having trouble finding tyres for the GLA's 19" wheels. Have found more options if I go to 245/40 rather than 235/45. There is a 2.28% difference on paper. Would this pose any problems?

Thanks in advance.
I replaced all four with the Goodyear Kelly Edge size 235/45R19 and could not be happier. I paid $700 including installation.
 

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Edit for clarity, it makes total sense that a tire with higher sidewalls or very thin sidewalls will have better small bump compliance. Ditto with having non-performance oriented suspension. It’s just not the application here. It also doesn’t make sense to call the GLA45 an SUV. Does even a single org consider the GLA an SUV besides MB corporate?

Agree totally on the example with the Metris. Again, using a stiff sidewall tire (or any tire selection factor that reduces sidewall stiffness) would probably reduce small bump compliance. Probably important in a Metris!

Can anyone imagine a Metris with 5” of ground clearance, suspension as stiff as the GLA, and rubber-band tires? Ha! How about the GLC? The only SUV seen round here like that are some Model X’s. They do look silly like that, tho cannot comment on drive quality.

It’s all good audi, we won’t have to drive each others cars, whether the roads are wet, dry, rough, or smooth!
I know I overstated my case. I was just surprised someone wanted to go with lower tires on this already low application. With the gift of experience, and dealing with older vehicles that call for 65 series tires, I've had universal success with the "+0" sizing approach.

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I just didn't want other members to blunder into this without careful analysis. Generally you find better deals on larger sizes. I just ordered some deep snows for the wife's Golf SW 4Motion 6-sp:love: Stock 205/55-16 doesn't make for meaty tires, she's currently using oversize 235/45-17 instead of stock 225/45-17 and it's awesomely smooth and solid. It doesn't matter to us how her g-force skidpad numbers are affected, it could go either way.

What I did was order 205/60-16 for her factory wheels. at 3% taller, it's a lot bigger, but consider the mission profile, snowy back roads and a log uphill driveway. No she didn't get the lifted Alltrack package for a multitude of reasons, but this tire size will help out a bunch of ways, inc ride verses the puny 205/55-16. I did want 215/55-16 but look at what I paid....$227!
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No way would less of a tire than 205/55-16 make any sense at all. That's where I am at. The 60s will be like balloony SUV tires, but that's what will work for us. I won't be installing them right away, her one 17" set is oversize Nexen Winguard S2 sport snows and the other set stock 225/45-17 Cooper CS5 Ultra I had leftover from my C240. Yes, a girl with 3 full sets....I have 3 sets too.
 

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It's so so important to consider application.

"hey, look at this car with rubber band tires that have super-stiff side walls and ridiculously sticky rubber compound, one click harder than racing slicks. The car lives in sunny California, will never see inclement weather, and is dying for some track time."

"That's dumb. You should be installing oversized all-weather or snow tires so you can drive over speed bumps and potholes more comfortably since you'll be driving in parking lots more than on the track. Your tires will last longer too and be cheaper. Look at this full size SUV, truck, and car parked on grass, to illustrate the point."

I get it, I really do. But there is a huge application disconnect. From my perspective, based on everything you've said, I STILL get a small-bump compliance benefit even running undersized tires compared to other GLA owners who use the correct size tires simply by nature of running OEM 19" wheels instead of OEM 20" wheels. At one point I believe you suggested we should change out wheels to 18's! It's simply prioritizing one set of goals vs another.

Those dogs do look ridiculously happy.
 
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