Tire Settings

Any discussion on using LapTimer. Please use this forum in case you need guidance on how to use LapTimer or perform a certain operation
Post Reply
recampbelljr
Fewer than 10 Posts
Fewer than 10 Posts
Posts: 1
Joined: Fri Oct 13, 2017 7:06 pm

Tire Settings

Post by recampbelljr »

I'm just setting this up, so I may be making a simple mistake.

When I go to insert my tire codes, it doesn't seem to have an option for the tires I'm running. (I'm running Dunlop Racing tires -- 450L15 in the front, and 500L15 in the rear.

Is there a way to insert these sizes?

https://flic.kr/p/Y1Mxv1
User avatar
Harry
Site Admin
Site Admin
Posts: 10518
Joined: Sun Sep 12, 2010 10:32 am
Location: Siegum, Germany
Contact:

Re: Tire Settings

Post by Harry »

Good point :-) Racing tires often use manufacturer specific codings. I'm not deep in that topic, but the result is you need to convert the dimensions to the road tier notation standardized and used within LapTimer. This is a sample from wikipedia
When referring to the purely geometrical data, a shortened form of the full notation is used. To take a common example, 195/55R16 would mean that the nominal width of the tire is approximately 195 mm at the widest point, the height of the side-wall of the tire is 55% of the width (107 mm in this example) and that the tire fits 16-inch-diameter (410 mm) wheels. The code gives a direct calculation of the theoretical diameter of the tire. For a size shown as "T/A_W" use (2×T×A/100) + (W×25.4) for a result in millimeters or (T*A/1270)+ W for a result in inches. Take the common example used above; (2×195×55/100)+(16×25.4) = 621 mm or (195×55/1270)+16 = 24.44 inches.
So you need to either investigate how your tire's coding works or just measure dimensions T, A and W and use these in LapTimer. A is derived by measuring the height of the side wall S and make A = S/T*100. The letter for speed rating is not relevant for LapTimer, set it to any value.

- Harry
Image Image Image Image
User avatar
Mateusz
20 or more Posts ★★★
20 or more Posts ★★★
Posts: 89
Joined: Mon Jul 03, 2017 8:32 pm

Re: Tire Settings

Post by Mateusz »

And just to clarify, if I am using a bigger or smaller than stock tire, what will entering the right info in the vehicle config change? Do I still need to enter the OBD wheel speed multiplier?

I guess there could be a flashing warning when speed exceeds tire rating - that's for autobahn driving on H-rated winter tires on the way to the Ring...
Last edited by Mateusz on Thu Oct 19, 2017 7:34 pm, edited 1 time in total.
User avatar
Harry
Site Admin
Site Admin
Posts: 10518
Joined: Sun Sep 12, 2010 10:32 am
Location: Siegum, Germany
Contact:

Re: Tire Settings

Post by Harry »

Changing the wheel size will change OBD speed values. So in case you are calibrating OBD speeds manually (Speed Multiplier), you need to adjust these when changing wheels. That's the same when tires wear off by the way... I may add an automatic calibration in the future ;-)

NB: Tire size is used for gear calculation and car visualizations (iOS) only.
Image Image Image Image
Post Reply