Bobbeh Posted February 23, 2008 Share Posted February 23, 2008 Went out with the GPS this evening to see how far out my speedo is on my 18s... 26 mph on gps = 30 on speedo 30 = 34 59 = 70 I used the cruise control to keep the speed the same throughout the test. Anyone else done this? Might have to put back on the 17s and see how it is then. Quote Link to comment Share on other sites More sharing options...
Pig Posted February 23, 2008 Share Posted February 23, 2008 17" - 100speedo about 85-90 GPS cant remember exactly as i havent done it in ages Quote Link to comment Share on other sites More sharing options...
juanchan Posted February 23, 2008 Share Posted February 23, 2008 I've had a GPS in both my cars, and both over-read. Corsa: GPS = 63, Speedo = 70 Supra: GPS = 65/66, Speedo = 70 Also, at Santa Pod, according to my speedo I terminal at about 110, but officially I'm at about 100. Edit to add I'm on 18's too. Quote Link to comment Share on other sites More sharing options...
miko_supra Posted February 23, 2008 Share Posted February 23, 2008 Went out with the GPS this evening to see how far out my speedo is on my 18s... 26 mph on gps = 30 on speedo 30 = 34 59 = 70 I used the cruise control to keep the speed the same throughout the test. Anyone else done this? Might have to put back on the 17s and see how it is then. thats pretty much how mine is on 17" Quote Link to comment Share on other sites More sharing options...
GazB Posted February 23, 2008 Share Posted February 23, 2008 Your figure seem about the same as what my speedo is reading against what my sat nav gps says. Shouldn't get a speeding ticket if i drive at the speeds that my speedo is saying, i'll just pi*s other drivers off going so slow Quote Link to comment Share on other sites More sharing options...
Bobbeh Posted February 23, 2008 Author Share Posted February 23, 2008 Yeah this is why I took it out and did a test, I usually get people sitting up my ass in built up areas and the like but no wonder as im doing like 26 in a 30, on the bright side theres no way of getting a ticket. I'm gonna take out my Civic tommorow and compare Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted February 23, 2008 Share Posted February 23, 2008 Same as mine on 18's, I think about 12% over. Quote Link to comment Share on other sites More sharing options...
Homer Posted February 23, 2008 Share Posted February 23, 2008 On my old car the speedo overead by about 7% throughout the range. 100 on the dial was 93 on the gps, 'm' on the dial was 198 on the gps Thats with stock wheels and tyre sizes Quote Link to comment Share on other sites More sharing options...
SUPRASUZUKI Posted February 23, 2008 Share Posted February 23, 2008 With new 285-35 tyres on 18's - 80 on the speedo = 81 on the GPS. Quote Link to comment Share on other sites More sharing options...
Gazboy Posted February 23, 2008 Share Posted February 23, 2008 Bobbeh I'll let you know what a real 150 is on the speedo in two weeks time at Vmax. Quote Link to comment Share on other sites More sharing options...
Shadow Beast Posted February 23, 2008 Share Posted February 23, 2008 the GPS readings and speedo is not to far out on ours what really is is the odometer, 15 km on the GPS and only 10 on the odometer!!!!!!!!! plus side is that at least the mleage will be low when we sell it!!! down side is a bugger to work out fuel consumption! richie Quote Link to comment Share on other sites More sharing options...
SteveR Posted February 23, 2008 Share Posted February 23, 2008 On the stock 16"s my old Supe had, the speedo agreed with the GPS at any speed. Quote Link to comment Share on other sites More sharing options...
Jake Posted February 23, 2008 Share Posted February 23, 2008 Of course it's the tyre size that affects the speedo reading, rather than the wheel size. Mine is pretty much spot on but then I don't have a DSC, the Motec does all that stuff. Quote Link to comment Share on other sites More sharing options...
Stevie72 Posted February 23, 2008 Share Posted February 23, 2008 170mph on speedo = 156 mph on private track. 100mph on speedo - 92 mph about 10% out Quote Link to comment Share on other sites More sharing options...
SteveR Posted February 23, 2008 Share Posted February 23, 2008 Of course it's the tyre size that affects the speedo reading, rather than the wheel size. Yeah sorry I meant stock 16" rims and stock tyre size on them, too. Quote Link to comment Share on other sites More sharing options...
Bobbeh Posted February 23, 2008 Author Share Posted February 23, 2008 With new 285-35 tyres on 18's - 80 on the speedo = 81 on the GPS. Mine are worn 285/30s on the back, what are the lower speeds like on yours? I was thinking that at certain speeds you'd get more accuracy... maybe the higher the better it will read, obviously not too keen in testing that out on the roads Gaz, have fun - I'll guess around 160-5 on the clock Quote Link to comment Share on other sites More sharing options...
Jake Posted February 23, 2008 Share Posted February 23, 2008 Yeah sorry I meant stock 16" rims and stock tyre size on them, too. It wasn't you I meant specifically Steve, one of the other replies mentioned 17" wheels but like I said, it's not the wheels that matter. PS & OT I've just seen your email, will reply shortly. Quote Link to comment Share on other sites More sharing options...
SteveR Posted February 23, 2008 Share Posted February 23, 2008 It wasn't you I meant specifically Steve, one of the other replies mentioned 17" wheels but like I said, it's not the wheels that matter. PS & OT I've just seen your email, will reply shortly. No worries, you're right though so I was just adding in that extra, important detail. OT - Cool Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 23, 2008 Share Posted February 23, 2008 Interestingly, the vehicle speed sensor reading on mine is within 0 to 2mph of the road angel (depending on how old the tyres are) all the way up to north of 170mph, yet the speedo still has that error built in Are they deliberately nerfed perhaps? Speedo needle is in a different time zone at 170+mph btw -Ian Quote Link to comment Share on other sites More sharing options...
SUPRASUZUKI Posted February 23, 2008 Share Posted February 23, 2008 Mine are worn 285/30s on the back, what are the lower speeds like on yours? I was thinking that at certain speeds you'd get more accuracy... maybe the higher the better it will read, obviously not too keen in testing that out on the roads I'll have a check tomorrow mate. Quote Link to comment Share on other sites More sharing options...
SUPRASUZUKI Posted February 24, 2008 Share Posted February 24, 2008 Just checked, both are equal at 30. Quote Link to comment Share on other sites More sharing options...
Pete Posted February 24, 2008 Share Posted February 24, 2008 All cars are generally out by 8% or so in my tests. My Supra is spot on with stock wheels, I think the SpeedM8 convertor has been programmed well. Quote Link to comment Share on other sites More sharing options...
Scott Posted February 24, 2008 Share Posted February 24, 2008 Checked mine quite a few times GPS 30 = Speedo 31/32 GPS 60 = Speedo 65 GPS 90 = Speedo 98/99 I have 18's on but i can't remember the tyre sizes. Rolling rad can't be far from stock as that seems about the right amount of error. Scott =op Quote Link to comment Share on other sites More sharing options...
ADL Mark Posted February 24, 2008 Share Posted February 24, 2008 On 275/35R18's my speedo reads out by near as dammit 10% as far up as I've been (an indicated 175). Interesting when I had the Apexi AVC-R wired up it was almost identical to the GPS reading so I agree with Ian that I think the speedo dial is designed to over-read, probably for some kind of safety? Quote Link to comment Share on other sites More sharing options...
JamieP Posted February 25, 2008 Share Posted February 25, 2008 19" 315 tyres, speedo indicated 180mph gps 162mph. Quote Link to comment Share on other sites More sharing options...
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