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New owner of Super 7 SV, tire questions


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Hello all,

 

I bought my first 2002 Caterham 7 SV last week and have some tire questions. It only took 41 years to pull the trigger....

My wants are for a daily driver, not a weekend warrior.  I live on the California coast so I have lots of options...

 

Currently the car has 7"x15" wheels in front and 8"x15 rears running Avon AC B10s  195/45-15 78V in front and 215/40-15 78Vs rear.  The tires are 7+ years old.  The speedometer is displaying my driving speed around 10 percent high.  Speedometer indicates 62 MPH, actual is closer to 55MPH for example.

Questions:  Where would I find out what the stock wheel and tire sizes?

                     Where/how does 7s read tire speed for the speedometer?

                     Would having 195/45s and 215/45 in back help fix the speedo error?

                     Any comments/recommendations would be appreciated

 

thanks

 

dl

 

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Congratulations on your purchase.  I can relate to your wait of 41 years--I test-drove a Caterham in 1978 but didn't get mine until 2007.

My 2007 SV came with 14 inch rims and 185/60 R14s front and rear.  The "stock" tire was Avon ZV3s, a great tire for the road.  I am not sure that "stock" ever applied to Caterham/Caterham USA, but more accurately, "original equipment" for a particular car.  For the road, tire choice should consider that the Seven can hydroplane easily in heavy rain.  I think the 15s would look better as in better filling the wheel wells, esp. in the rear, and are more widely available than 14s.  Good luck in your search.

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What type of speedo do you have?  When I bought my Westfield (the first time) the speedo read very high. It's a Smith's mech unit, like MGB.

Dave Bean put me onto a shop on the west coast --maybe Palo Alto Speedo--

they asked how many turns the cable did in a given distance, and re-geared the unit to suit

So, if this service is still available, get the tires you want, and match the speedo to them

also, back in "the day", a shop could build you a correction gearbox that went in the cable

 

Edited by 7Westfield
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You can search for Speedometer Correction Box.  Here's one example:

 

https://speedometercablesusa.com/gear_box_adapters.html

 

Back in the day, these things were used a lot for calibrating odos for rally.  Don't remember the brand we used.  Pretty crucial if the navigator gets "lost" in a stage.

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2 hours ago, 7Westfield said:

What type of speedo do you have?  When I bought my Westfield (the first time) the speedo read very high. It's a Smith's mech unit, like MGB.

Dave Bean put me onto a shop on the west coast --maybe Palo Alto Speedo--

they asked how many turns the cable did in a given distance, and re-geared the unit to suit

So, if this service is still available, get the tires you want, and match the speedo to them

also, back in "the day", a shop could build you a correction gearbox that went in the cable

 

The speedometer is labeled  "Caterham"  I'm thinking (right or wrong) of trying to correct the problem through tire size, since I need to replace the rubber anyway. 

The first 7 I drove was at Dave Bean down in Goleta/Santa Barbara in 1981 or 82.  I remember having Fry Boots on at the time, very memorable drive.

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Have you reviewed if the dip switches can be adjusted? 

 

My speedometer never worked so I have a speedhut GPS replacement but I believe you can adjust how the speedometer reads out without changing rubber. 

 

https://www.caterhamlotus7.club/forum/techtalk/speedo-inaccuracy

 

If you have the Caerbont speedometer this is their calibration procedure for the 8 switch model. (pdf warning) 

 

https://www.classicinstruments.com/userfiles/files/Manuals/8 Pulse Speedometer Calibration Instr.pdf 

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On 11/8/2021 at 5:39 AM, Taber10 said:

Congratulations on your purchase.  I can relate to your wait of 41 years--I test-drove a Caterham in 1978 but didn't get mine until 2007.

My 2007 SV came with 14 inch rims and 185/60 R14s front and rear.  The "stock" tire was Avon ZV3s, a great tire for the road.  I am not sure that "stock" ever applied to Caterham/Caterham USA, but more accurately, "original equipment" for a particular car.  For the road, tire choice should consider that the Seven can hydroplane easily in heavy rain.  I think the 15s would look better as in better filling the wheel wells, esp. in the rear, and are more widely available than 14s.  Good luck in your search.

What wheels are you running on your SV?  Do you know what the offset is on your wheels, I'm thinking of changing out the set.

 

thanks

 

dl

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On 11/8/2021 at 10:16 AM, sltous said:

Have you reviewed if the dip switches can be adjusted? 

 

My speedometer never worked so I have a speedhut GPS replacement but I believe you can adjust how the speedometer reads out without changing rubber. 

 

https://www.caterhamlotus7.club/forum/techtalk/speedo-inaccuracy

 

If you have the Caerbont speedometer this is their calibration procedure for the 8 switch model. (pdf warning) 

 

https://www.classicinstruments.com/userfiles/files/Manuals/8 Pulse Speedometer Calibration Instr.pdf 

Thanks for the info, currently looking at the tire solution first, it needs new shoes.  Then if need be I will delve deeper

 

dl

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  • 2 weeks later...
On 11/8/2021 at 1:16 PM, sltous said:

Have you reviewed if the dip switches can be adjusted? 

 

My speedometer never worked so I have a speedhut GPS replacement but I believe you can adjust how the speedometer reads out without changing rubber. 

 

https://www.caterhamlotus7.club/forum/techtalk/speedo-inaccuracy

 

If you have the Caerbont speedometer this is their calibration procedure for the 8 switch model. (pdf warning) 

 

https://www.classicinstruments.com/userfiles/files/Manuals/8 Pulse Speedometer Calibration Instr.pdf 

 

My speedo never work also. After a comprehensive as well speeo replacement.  I  found that who ever manufactured the wiring harness for Caterham during the assembly place the wiring spade connectors  in the wrong sequence on the speedo connector. Their for, the speedo couldn't read the plus from the transmitter at gearbox correctly. Also, the LED alternator warning bulb in speedo wouldn't work correctly also warning light stayed on constantly. The wiring harness needed a resister in order to properly function on speedo correctly for LED bulbs. 

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