Go Back   986 Forum - for Porsche Boxster & Cayman Owners > Porsche Boxster & Cayman Forums > Boxster General Discussions

Reply
 
LinkBack Thread Tools Display Modes
Old 04-06-2011, 06:31 PM   #1
Registered User
 
Idaho Red Rocket 3's Avatar
 
Join Date: Oct 2010
Location: Nampa, ID.
Posts: 488
New Front Tires - Question

I'll be ordering new front tires this week. My 2000 S came with 17 inch wheels and 205/50ZR17 tires. I am thinking of replacing with 225/45ZR17. The rears are 255/40ZR17.

What are the positive benefits ?

What are the negative drawbacks ?
Idaho Red Rocket 3 is offline   Reply With Quote
Old 04-06-2011, 07:18 PM   #2
Track rat
 
Topless's Avatar
 
Join Date: Nov 2006
Location: Cucamonga CA
Posts: 3,655
Garage
Better front grip, shorter braking distance, less understeer are all positives.

Slightly more prone to hydroplane through standing water is a negative.
__________________
2009 Cayman 2.9L PDK (with a few tweaks)
PCA-GPX Chief Driving Instructor
Topless is offline   Reply With Quote
Old 04-06-2011, 09:18 PM   #3
Certified Boxster Addict
 
Join Date: Nov 2010
Location: Los Angeles
Posts: 7,475
Here is my experience in switching from 205/50/ZR17 to 225/45/ZR17 on the fronts of my '99 (rears remain at 255/40/ZR17);

Pros:
- Much better overall grip
- Much less understeer
- No wheel, body or suspension fitment issues on stock wheels
- Speedo/ABS unaffected
- Looks better

Cons:
- Slightly slower turn-in
- Slightly more expensive

No Difference (that I can tell):
- Braking performance/distance
- Hydroplaning in the rain on the freeway

Overall, what I noticed the most was that the 205's would turn in quickly and then plow with understeer through the turn whereas the 225's turn in slower but are able to carve the turn much better. The 225's still understeer when pushed but not nearly as soon as the 205's did. Car is much better balanced with the 225's.

I'd highly recommend the 225's in front.
__________________
1999 996 C2 - sold - bought back - sold for more
1997 Spec Boxster BSR #254
1979 911 SC
POC Licensed DE/TT Instructor
thstone is offline   Reply With Quote
Old 04-07-2011, 07:35 AM   #4
Track rat
 
Topless's Avatar
 
Join Date: Nov 2006
Location: Cucamonga CA
Posts: 3,655
Garage
Quote:
Originally Posted by thstone
No Difference (that I can tell):
- Braking performance/distance
- Hydroplaning in the rain on the freeway
These are just physics 101. Braking distance is primarily a function of weight and tire grip. Any improvement in front tire grip where 80% of your braking forces happen and you will shorten your stopping distance. For a real eye opener, mount a pair of 255/40/17 R-comp tires to the front and compare your stopping distance... WOW!

Hydroplaning is the opposite effect. It is a function of speed, weight, and contact surface area for a given tire compound and tread pattern. All tires will hydroplane at some speed. Increasing tire contact surface area (wider tire) will result in hydroplaning at a lower speed through standing water. For a real eye opener again, mount those 255 R-comps to the front (very high contact surface area) and go out blasting through puddles on the next rainy day. WOW! Surf City!

My 205 PS2 street tires will hydroplane at around 65mph, 225 PS2s will hydroplane at around 57mph, my 255 R-comps will hydroplane at 40mph.

A good link:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=16
__________________
2009 Cayman 2.9L PDK (with a few tweaks)
PCA-GPX Chief Driving Instructor

Last edited by Topless; 04-07-2011 at 07:42 AM.
Topless is offline   Reply With Quote
Old 04-07-2011, 11:00 AM   #5
Certified Boxster Addict
 
Join Date: Nov 2010
Location: Los Angeles
Posts: 7,475
All I was saying is that I personally didn't notice any difference in braking or hydroplaning when the only change was going from 205 to 225 - everything else stayed the same (same tire mfg, model, compound, brakes, etc).

But you are absolutely correct that there should be (or is) an improvement in braking and some increase in hydroplaning due to increase in width of the 225.

The main point is that I've found the 225's to be a great improvement over the 205's.
__________________
1999 996 C2 - sold - bought back - sold for more
1997 Spec Boxster BSR #254
1979 911 SC
POC Licensed DE/TT Instructor

Last edited by thstone; 04-07-2011 at 12:09 PM.
thstone is offline   Reply With Quote
Old 04-07-2011, 12:57 PM   #6
Registered User
 
Idaho Red Rocket 3's Avatar
 
Join Date: Oct 2010
Location: Nampa, ID.
Posts: 488
Thank you Gentlemen.

Your answeres were exactly what I expected base on experiance with other vehicles. I beleived they would fit based on the allowed sizes for 18" wheels on the 986. But I really needed to hear someone say they have done it, the tires fit, they liked it, and with no real problems.

Tires are now on order. I ordered a new matching set of 255 for the rear too.

Thanks, Bill.
Idaho Red Rocket 3 is offline   Reply With Quote
Old 04-09-2011, 04:35 PM   #7
Registered User
 
Join Date: Jan 2008
Location: atl
Posts: 363
if 225 are better, how come they didn't come stock?

will 225 fit on 17" with only 7" width without any problems?
__________________
-Tuan
tuanle16@juno.com
tuanle16 is offline   Reply With Quote
Old 04-09-2011, 08:56 PM   #8
Registered User
 
Idaho Red Rocket 3's Avatar
 
Join Date: Oct 2010
Location: Nampa, ID.
Posts: 488
That is a good question. The new tires went on the car this morning. Fit is fine, no problems. Handling is much improved and car is rolling smother and the squirm is gone. I think it could be due to the less differance in the front to rear size. 205/255 is 50 milimeters differance and 225/255 is 30 milimeters. My '98 has 205/225 front/rear and is very steady, stable and smooth, even at over 150 mph. I haven't had the S over 125 mph becauase of the squirm. Its time to see what S can do.
Idaho Red Rocket 3 is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -8. The time now is 01:29 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page