#1 Replacing Tyres and Speedometer Recalibration
Posted: Fri Apr 18, 2008 10:45 am
Many people consider changing the tyres on their cars to a lower profile than the standard 185's. Reasons vary from "it looks better" to "they cost less" the later being particularly true. The cost of a Michelin 185VR15 is about ?200 and Vredestein ?95, whereas a modern Pirelli P6000 205/65 VR15 is about ?55 fitted (avoid the P4000!). Given the tyres need to be changed every 5 years, regardless of mileage and wear, there is plenty of incentive to move to the newer and more available product.
If you go down this route you really should have the speedometer re-calibrated and you will need to do the following.
1. Disconnect the flexible drive from the speedometer
2. Make a cardboard 'arrow' and press on the end of the inner cable
3. Jack up one side of the car, put blocks on the other wheels, gears in neutral
4. Mark jacked rear tyre with chalk line or masking tape
5. Mark body with masking tape corresponding to the mark on the tyre
6. Turn driving wheel exactly 20 times while an assistant counts the number of complete turns the cardboard arrow makes, to the nearest 1/8 of a turn
7. Note make and size of tyre.
Speedograph Richfield http://www.speedograph-richfield.com/ will do the re-calibration for you (they operate a mail order service) and they will need:
a) The number of turns of inner cable for 20 turns of the drive wheel e.g. 13.75
b) Make and size of drive wheel tyre e.g. Yokohama TWI 205/65/15; dia. 647mm
c) Make and part number of speedometer e.g. Jaguar E-Type, SN .6322/09A; C25190
d) Is car fitted with a limited slip differential e.g. Yes
A tyre size calculator is available here: http://www.tyresave.co.uk/tyresize.html
The chronological age of any tyre can be found on the tyre sidewall by examining the characters following the symbol "DOT".
For tyres manufactured after the year 1999, the last four numbers identify the date of manufacture of the tyre to the nearest week. The first two of these four numbers identify the week of manufacture (which range from "01" to "52"). The last two numbers identify the year of manufacture (e.g., a tyre with the information "DOT XXXXXX2703? was manufactured in the 27th week of 2003). For tyres manufactured prior to the year 2000, three numbers instead of four indicate the date of manufacture. Also, during the early 1990?s, Continental added a triangle (◄) to the end of the character string to distinguish a tyre built in the 1990?s from previous decades. (e.g., a tyre with the information "DOT XXXXXX274◄? was manufactured in the 27th week of 1994).
Any tyres (including the spare) with a DOT number earlier than XXXXXX1603 should now be changed regardless of mileage - 5 years is the maximum age. You should also be aware in the event of an accident any tyres beyond their recommended expiration date, or of the incorrect speed rating, could be grounds for voiding your insurance claim - regardless of the speed you were traveling at the time. All E-Types must be fitted with V rated tyres (149mph). I have seen many cars fitted with H rated tyres (130 mph) but as Jaguar made great claim as to the E-Types maximum 150mph speed these are deemed 'incorrect'. Worth checking if you are buying a car - good grounds for reducing the price!
There is a pressure rating on the sidewall e.g. 44psi - this relates to the maximum pressure the tyre should be inflated to - not the running pressure (typically 32-34psi for an E-Type).
In the UK you can be fined and your licence endorsed for each tyre that fails to comply with tread, pressure, speed rating and age recommendations. It is no excuse to say "I only ever drive at a maximum of XX mph". Always pays to be nice to the Policeman if you are stopped for any reason!
David
If you go down this route you really should have the speedometer re-calibrated and you will need to do the following.
1. Disconnect the flexible drive from the speedometer
2. Make a cardboard 'arrow' and press on the end of the inner cable
3. Jack up one side of the car, put blocks on the other wheels, gears in neutral
4. Mark jacked rear tyre with chalk line or masking tape
5. Mark body with masking tape corresponding to the mark on the tyre
6. Turn driving wheel exactly 20 times while an assistant counts the number of complete turns the cardboard arrow makes, to the nearest 1/8 of a turn
7. Note make and size of tyre.
Speedograph Richfield http://www.speedograph-richfield.com/ will do the re-calibration for you (they operate a mail order service) and they will need:
a) The number of turns of inner cable for 20 turns of the drive wheel e.g. 13.75
b) Make and size of drive wheel tyre e.g. Yokohama TWI 205/65/15; dia. 647mm
c) Make and part number of speedometer e.g. Jaguar E-Type, SN .6322/09A; C25190
d) Is car fitted with a limited slip differential e.g. Yes
A tyre size calculator is available here: http://www.tyresave.co.uk/tyresize.html
The chronological age of any tyre can be found on the tyre sidewall by examining the characters following the symbol "DOT".
For tyres manufactured after the year 1999, the last four numbers identify the date of manufacture of the tyre to the nearest week. The first two of these four numbers identify the week of manufacture (which range from "01" to "52"). The last two numbers identify the year of manufacture (e.g., a tyre with the information "DOT XXXXXX2703? was manufactured in the 27th week of 2003). For tyres manufactured prior to the year 2000, three numbers instead of four indicate the date of manufacture. Also, during the early 1990?s, Continental added a triangle (◄) to the end of the character string to distinguish a tyre built in the 1990?s from previous decades. (e.g., a tyre with the information "DOT XXXXXX274◄? was manufactured in the 27th week of 1994).
Any tyres (including the spare) with a DOT number earlier than XXXXXX1603 should now be changed regardless of mileage - 5 years is the maximum age. You should also be aware in the event of an accident any tyres beyond their recommended expiration date, or of the incorrect speed rating, could be grounds for voiding your insurance claim - regardless of the speed you were traveling at the time. All E-Types must be fitted with V rated tyres (149mph). I have seen many cars fitted with H rated tyres (130 mph) but as Jaguar made great claim as to the E-Types maximum 150mph speed these are deemed 'incorrect'. Worth checking if you are buying a car - good grounds for reducing the price!
There is a pressure rating on the sidewall e.g. 44psi - this relates to the maximum pressure the tyre should be inflated to - not the running pressure (typically 32-34psi for an E-Type).
In the UK you can be fined and your licence endorsed for each tyre that fails to comply with tread, pressure, speed rating and age recommendations. It is no excuse to say "I only ever drive at a maximum of XX mph". Always pays to be nice to the Policeman if you are stopped for any reason!
David