How big tires can you actually fit?

[Adrian]

As mentioned in another thread, today I tried with some 235/60/18s. Didn't work out. The fronts were rubbing on the spring. Much is good, but in this case much wasn't better
How big can you go? Didn't seem like I needed to go down that much, I think 235/55/18 will fit. Thinking about that or 245/50/18. Any thoughts?

EDIT: It was touching right below where the tire sidewall "changes", very near the middle of the sidewall.

[haoz129]

Hi Adrian

Enjoy your threads, including the youtube,

Can't give you any solution since I haven't gone as far as you did.
But I'd like provide some idea since I'm going to try these:
1) Upgrade to Brembo Caliper with stock rotors & pads;
2) Use XC90 Atlantis 18" rim with 20mm H&R TRAK+ spacers;
3) Upper size tire to 225/60R18 Michelin Primacy MXV4 which is larger 20.65mm than stock in radius;

I saw you are using Brembo, nice move but hope your rim don't have offset issue for those big calipers. I have to use spacers thicker than 18mm to provide axial clearance since I chose Atlantis which has offset 49mm.

According to the tire rubbing you have I just went out and measured the gap between the front spring seat and tire. For a new stock tire the gap is around 25mm. But the difference between stock and your 235/60R18 is 26.65mm in radius. So there isn't enough clearance for an XC70, mine is 2003, up that much to accomodate an XC90 tire. Hope this explains your rubbing issue.

I prefer big tires since large foot meet the outlook of an XC70 and it provide more comfortable ride. And I like Michelin Primacy MXV4.
But for 18" MXV4 225/55 & 225/60 are the only choices meet loading requirement. No 235 but I think 225 is wide enough for me.
It does surprised me that 225/60R18 is much cheaper than 225/55R18. Don't know why. Sure definitely go to the bigger one and up further.

As others commented:
Different tire size impact speedo;
Large tire decrease the acceleration power, especially start from a stand still;
Risk of rubbing.

We are benefitting from plenty of cleanrance XC70 provided. So we have more freedom to upper size the tire if we could translate-read the speedo and not sensitive about the acceleration power, .

Hope after I mount 225/60R18 I can still steer fully without rubbing front-inner well.

By the way, I have asked Chilled Man and ifnt420 for advices about my new brake design. They are very knowledgable about brake, rim, tire...
Maybe you could ask and then make decision.

Howard
_______________
2003 XC70 165Km

[Adrian]

Thankyou! Enjoying the reply!

Ocean Racer also gave me a tip about using spacers. I found a page here in norway wich can deliver within a few days. However, i'm thinking that the rears may rub against the plastic due to the oversized tires. What do you think? The spacers are 1200 NOK (~200 USD)

He also gave me another link to this thread:
http://www.volvoxc.com/forums/showthread.php?t=12285
Wich is about Adelaide fitting 235/65/17 tires. However, those are used tires - and he had to modify the plastic a bit to make them fit. He also states that there is no way he'd get on a new set of those same tires.

I've attached five images. First one is Adelaides car with mentioned 235/65/17 tires, second is my 235/60/18 tires on my car (in the air). This is where i think it will get tricky. Look at the right side (forward on the car) (and last image) of the rear tires. They are "almost" touching already. Or..? I say "almost" because there is some room left. And i think it will work if i use Adelaides trick. Rest of the images is just.. more images of the insanely huge tires and cool rims.

EDIT: 235/60/18 is 1.3mm more in diameter, and 5.97mm more in rolling distance than 235/65/17, for those who doesn't know.

[Adrian]

More images (for those to lazy to check Adeleides thread.) Look at how tight that rear tire is. Any way of moving it backwards a bit?

[Ocean Racer]

I tried 245/45/20
Doesnt fit. (too wide by atleast an inch)

BTW, you MUST keep your 'plus sizing' formula when installing bigger wheels.
If not, you seriously run the risk of blowing your diffs.

[haoz129]

Hi Adrian

Don't let my spacers confuse you and I don't think the spacers will solve your rubbing issue.
Sorry for my objection, Ocean Racer.

First let's see why your front tire is rubbing:
Base on my measurement and calculation for a new stock tire there is a gap between spring seat and tire tread surface which is around 25mm. That's why the stock tire won't meet the spring.
But your 235/60R18 is 26.65mm taller than the stock one in radius. That's why it will hit the spring since there isn't enough radial clearance to accept the big rubber. This is still the best scenario since I meansured when the car steered center. The rubbing will get worse when you steer away from center.

Second let's see the 2 available solutions:
1) Lower the tire:
- 235/65R17 is taller than stock tire 25.7mm in radius, it won't work either. But for Adelaide's worn tire it works since the tire shrinked;
- 245/50R18 is taller than stock tire 8.15mm in radius, it will work;
- 225/60R18 is taller than stock tire 20.65 in radius, it will work, but with some risk in case any tire distortion existed;
2) Move tire outward/away from the spring. As I measured for a 215 width tire you need move the tire outward 45mm to make sure the tire side wall won't touch the spring. So for 235 width tire you need move 10mm more then it comes to 55mm outward needed. This is not a 5/10mm spacer can help. Unless you have a rim with much less offset than the stock rim which could help moving the tire outward already. And I won't think about to add 55mm spacer only for welcomnig big tires.

For sure there are more points will rubbing other then the spring. I will concentrate more on the front. And I worry more when steer comes to a full turn.

Above all I prefer go to less taller tires.

Of cause, my assumption is base on:
- 2003 XC70;
- Your rim is similar size as 7" width, 18" diameter and 49mm offset. Which doesn't have a very small offset to put the rim/tire outward.

The last thing I want to mention is why the spacers introduced in my design. I think if you are going to use Brembo caliper this will help you as well.
The R caliper has much bigger size both radial and axial. Base on my measurement:
- 17" and up diameter rim will provide reasonable clearance for it in radial speaking. So I chose Atlantis which is 18".
- 40mm and up gap between hub and wheel spoke will be needed to clear the caliper in axial speaking. For Atlantis I only got 25mm gap. So I have to move the rim outward to clear the caliper. That's why I need 20mm spacers. This is for accomodate the caliper not for the tire.

Your new rims are very beatiful but I don't have the specification for them. And I am not sure whether they clear the R caliper well.
But I do want to mention please be very careful to use spacers in case you need them. There are lots of arguments about spacers. The most important 2 are:
- Will spacers introduce safty issues. I think if using properly there won't be safty issues. Keep these in mind: 1) Select high quality one which is designed for Volvo XC70, and the hub centric one, not a cheap and general one. 2) Always extend lug bolts as much as the width of the spacer. 3) Try every best to install your rim perfectly by making sure the hub, spacer and rim contact surface is clean. 4) Tight your bolt with proper pattern and torque.
- Will spacers lead prematual failure to hub bearing. I think under 25mm we won't worry too much. Try not go over 25mm.

Howard
___________________
2003 XC70 Blue 165Km

[Adrian]

I tried 245/45/20
Doesnt fit. (too wide by atleast an inch)

BTW, you MUST keep your 'plus sizing' formula when installing bigger wheels.
If not, you seriously run the risk of blowing your diffs.

20" on an XC70, nice..

Explain the formula?

First let's see why your front tire is rubbing:
Base on my measurement and calculation for a new stock tire there is a gap between spring seat and tire tread surface which is around 25mm. That's why the stock tire won't meet the spring.
But your 235/60R18 is 26.65mm taller than the stock one in radius. That's why it will hit the spring since there isn't enough radial clearance to accept the big rubber. This is still the best scenario since I meansured when the car steered center. The rubbing will get worse when you steer away from center.

Second let's see the 2 available solutions:

So, just keeping under 25mm more in radius (50 in diameter) will clear it OK?

How about 245/55/18? My calculator says 40.8mm more in diamter. Given what you have told me, it will be a tight fit - but it will fit.

EDIT: The rims are HEICO Volutions. 18x8"

[Forkster]

Adrian, you need to be using 235/50R-18 - and there are lots of options to choose from at TireRack as it's a very common size and it probably won't rub on your springs - again a spacer can help. I would not recommend any tire with a difference in 5% diameter. And if you're looking at the 245 - 245/45R-18 ONLY.

Here is how you find out what you can put on: http://www.miata.net/garage/tirecalc.html

Put in the VolvoXC70 OEM tire size: 215/65-16. If you want 245 width and the rim is 18", then the only valid size is 45. If you REALLY REALLY want to pimp out (you'll need spacers), 255/50-R18. Those will be very, ummmm, wide tires. Spacers WILL required but your Volvo will look like a Volvo-dragster.

[Adrian]

I'm not looking to pimp out. I'm looking to fill my wheelwells(?) as much as possible. As explained by Haoz it is in theory possible to increase the diamteer of the wheel up to 50mm without rubbing.

235/50/18: 0.92 % larger than original (Ø: +6.3 mm)
235/55/18: 4.34 % larger than original (Ø: +29.8 mm)

245/45/18: 1.2 % smaller than original (Ø: -8.2 mm)
245/50/18: 2.38 % larger than original (Ø: +16.3 mm)
245/55/18: 5.95 % larger than original (Ø: +40.8 mm)

Still holding on your 235/50R-18? If yes; i will respect your opinion and take it into consideration, but right now there are two people sort of saying two different things. One is safing and using an US-specific page (Norway allows up to 5% increase / decrease, with some slack, on cars with ABS), while one is giving me numbers. Are there US-rules that gets you to those numbers, or can fitting tires ~5% bigger actually hurt my car other than rubbing?

[Forkster]

245/45-18 is also a good bet - LOTS of tires made in that size at affordable prices.

The idea behind sizing is to get the tire that is a common size and offers the best performance, and stability but is closest in diameter to your OEM tires.