Just some random thoughts and suggestions... Kinda irritates me when folks are prepared to take people's hard earned for parts that are wrong for the vehicle, in this case 15" wheels for an X1/9. Dallara successfully modified the X1/9 for Group 5 in the seventies, they widened the track, lengthened the wheelbase, and lowered it 3" but they retained the 13" wheel, but 50 or 55 section road legal motorsport tyres didn't exist in period. Lotus pioneered the modern 13" motorsport tyre for the MK1 Lotus Elise - Avon ZZS. Best width of tyre for X1/9's with 150-200bhp is 185/55/13 front, 215/55/13 rear. These effectively lower the car, some, and the rest of the lowering is achieved by using a shorter strut. Springs wise, 175 lb/inch front, 225 lb/inch rear is fine. Fitting coilivers limits the suspension travel, with 225 lb/inch rear springs, you can jump up and down on the back and it scarcely moves. The original body has discrete factory flared arches and you can max out the front and rear track without modifying them other than rolling the internal edges. Do these things and the stance will be awesome and the car will be fast. Sorry but 15" will never look right on these and if something looks wrong chances are it is wrong for a reason. You won't be able to lower it much and even if you can get a 35 or 45 section tyre, the ride will be adversely affected. The smaller the circumference of the wheel plus tyre, the lower the inertia, this is good. Fit an Addco or equivalent front ARB. Replace the white nylon pedal box bushing with one made from SAE660 bearing bronze, eliminates all freeplay in the pedals. If you persevere with X1/9's you will fall back in love with 13" wheels eventually. You didn't make a mistake buying the car itself that's the main thing. Buy some more if you can you'll always break even. Start saving for a locking diff and some beefy close ratios because the standard cogs don't handle big increases in power reliably. Best of luck mate 👍
Wheels look ok, the car is sat higher overall, those VW Golf mk4/5 calipers are a good cheap option. Now you need an adjustable pedal box to move some of the braking effort to the rear. The fronts will lock up way too easy
Is this going to be a track car? The front tyre contact patch is too big for road use. On gravel or wet roads it won't steer. Also the tyres protrude too far to avoid hitting the guards (fenders) if you drive over a bump when the wheel is turned.
The beauty about being a X1/9 owner in 1979 was that you could buy Pirelli P6 tires in the stock 13 inch size and have all the tire you would ever need. Also I drove my off the lot and drove it like I stole it being a 19 year old kid. The brakes were more than enough and I cannot imagine needing more. The only thing that we all know about these sweet rides was lack of power. But the handling and braking was exactly what you needed.
I'll keep my 13s. You took a 70s sports car and turned it into a Civic. Now of course that is completely my opinion, and I really hope you disagree with me! I don't want your X to look like my X, imagine going to a car show and all the cars looked the same.
Just a thought, the 205 50 is much taller than the close to stock 185 60 13. top speed goes up but off the line will suffer. If you go with a 195 50 15 it is closer to the 13 Here are the numbers. 185 60 13 Dia. 21.74 Cir 68.3 Dia 7.25 mph 20 mph 70 speed for comparison 205 50 15 D 23.07 C 27.8 W 8.07 mph adjusted comp to 13 inch tire 20 74.25 21.22 74.28 195 50 15 D 22.68 C 71.24 W 7.68 Mph comp to 13 inch 20 70 21.25 72.03 Yokohama makes a 195 50 15 for about $88
I have a set of VAS Primas on the front of my ‘77 Series 1 and have the stud conversion, too. My only problem is that the Primas aren’t well matched with the standard X1/9 rears; the Primas clamp on pretty hard but the rears still spin freely. Apparently, using Fiat 125 / 132 / possibly 124 Spider rear callipers fixes this, as they have 38mm, pistons instead of the X1/9’s 34mm versions but are otherwise identical. It’ll be interesting to see if you also experience this.
