Matthew Abate

Okay, so that’s two people who have had success without modifying the brackets. That makes me wonder if it is just the Whitehead Performance brackets that need modifications. [mention=4648]SteveJ[/mention], can you show where you needed the spacers? I didn’t quite follow that part of your write up. Were they out on the sides? Sent from my iPhone using Classic Zcar Club mobile

After I noticed a comment on the WHP site about their 70-72 front bumper brackets about needing to heavily modify them to fit a 73 (https://whiteheadperformance.com/product/new-datsun-240z-260z-280z-stainless-steel-euro-bumpers/), I did a bunch of searches of this and other sites and haven’t been able to confirm that this is or isn’t true. I did find someone on ZCar.com saying that you have to do a bunch of work to make them fit, but in that same thread someone mentioned that the original 70-72 mounting points are still there and that the 73 bumper brackets mount in a different location (https://www.zcar.com/forum/10-70-83-tech-discussion-forum/321961-73-bumper-brackets.html#/topics/321961). This would make sense if the bodies are all the same globally and they just fit one style in the US and the other everywhere else. Does anyone have experience with this either way? Photos clarifying these points would be much appreciated. If anyone found that it IS necessary to modify the 70-72 brackets to fit a 73 please describe the work involved.

It’s also a good zen exercise for meditation purposes, considering cars are therapy. [emoji6]

In related news, Yokohama just brought back its 1981 Advan HF Type D tire: https://jalopnik.com/yokohama-brings-back-a-1980s-tire-so-you-can-make-your-1819844548 I would LOVE to get my hands on a set of these, but they seem to be JDM only.

Not by themselves, but as part of the complete job of reworking the head.

Polyester primed

Some progress:

You’re both wrong. That is the one homologated R390 that was made to allow the R390 GT1 to race. It’s a race car with stuff slapped on it to get around rules. https://en.m.wikipedia.org/wiki/Nissan_R390_GT1

I used 80% for the table because of that Michelin I found, but I can easily make a copy in other ratios. 634mm comes to 24.96” in diameter. I assume that different brands will get you different diameters, but the .165” difference between these and the Michelin is less than you lose before buying new tires so ¯\_(ツ)_/¯. Sent from my iPhone using Classic Zcar Club mobile

I put together a spreadsheet for 14 to 16" wheels that I hope does a better job of illustrating why I think this question of 175HR14 sidewall-ratio accuracy is important if you want speedometer accuracy. Width Ratio Rim Side Diam. Circ. R/Mi Δ Width Range 175 14 5.51 25.02 78.61 805.96 N/A 4.5 - 5 197 70 14 5.43 24.86 78.09 811.32 -0.67% 6 175 50 14 3.44 20.89 65.63 965.45 -19.79% 5 - 5.5 175 55 14 3.79 21.58 67.79 934.63 -15.96% 5 - 5.5 175 60 14 4.13 22.27 69.96 905.71 -12.38% 5 - 5.5 175 65 14 4.48 22.96 72.12 878.53 -9.00% 5 - 5.5 175 70 14 4.82 23.65 74.29 852.93 -5.83% 5 - 5.5 175 75 14 5.17 24.33 76.45 828.78 -2.83% 5 - 5.5 175 80 14 5.51 25.02 78.61 805.96 0.00% 5 - 5.5 185 50 14 3.64 21.28 66.86 947.60 -17.57% 5.5 - 6 185 55 14 4.01 22.01 69.15 916.24 -13.68% 5.5 - 6 185 60 14 4.37 22.74 71.44 886.89 -10.04% 5.5 - 6 185 65 14 4.73 23.47 73.73 859.37 -6.63% 5.5 - 6 185 70 14 5.10 24.20 76.02 833.50 -3.42% 5.5 - 6 185 75 14 5.46 24.93 78.30 809.15 -0.39% 5.5 - 6 185 80 14 5.83 25.65 80.59 786.17 2.46% 5.5 - 6 195 50 14 3.84 21.68 68.10 930.39 -15.44% 6 - 6.5 195 55 14 4.22 22.44 70.51 898.56 -11.49% 6 - 6.5 195 60 14 4.61 23.21 72.92 868.84 -7.80% 6 - 6.5 195 65 14 4.99 23.98 75.34 841.03 -4.35% 6 - 6.5 195 70 14 5.37 24.75 77.75 814.94 -1.11% 6 - 6.5 195 75 14 5.76 25.52 80.16 790.42 1.93% 6 - 6.5 195 80 14 6.14 26.28 82.57 767.33 4.79% 6 - 6.5 205 50 14 4.04 22.07 69.34 913.79 -13.38% 6.5 - 7 205 55 14 4.44 22.88 71.87 881.55 -9.38% 6.5 - 7 205 60 14 4.84 23.69 74.41 851.51 -5.65% 6.5 - 7 205 65 14 5.25 24.49 76.94 823.45 -2.17% 6.5 - 7 205 70 14 5.65 25.30 79.48 797.18 1.09% 6.5 - 7 205 75 14 6.05 26.11 82.02 772.54 4.15% 6.5 - 7 205 80 14 6.46 26.91 84.55 749.37 7.02% 6.5 - 7 215 50 14 4.23 22.46 70.57 897.77 -11.39% 7 - 7.5 215 55 14 4.66 23.31 73.23 865.17 -7.35% 7 - 7.5 215 60 14 5.08 24.16 75.89 834.86 -3.59% 7 - 7.5 215 65 14 5.50 25.00 78.55 806.60 -0.08% 7 - 7.5 215 70 14 5.93 25.85 81.21 780.19 3.20% 7 - 7.5 215 75 14 6.35 26.70 83.87 755.45 6.27% 7 - 7.5 215 80 14 6.77 27.54 86.53 732.23 9.15% 7 - 7.5 225 50 14 4.43 22.86 71.81 882.31 -9.47% 7.5 - 8 225 55 14 4.87 23.74 74.59 849.39 -5.39% 7.5 - 8 225 60 14 5.31 24.63 77.38 818.85 -1.60% 7.5 - 8 225 65 14 5.76 25.52 80.16 790.42 1.93% 7.5 - 8 225 70 14 6.20 26.40 82.94 763.90 5.22% 7.5 - 8 225 75 14 6.64 27.29 85.73 739.10 8.30% 7.5 - 8 225 80 14 7.09 28.17 88.51 715.86 11.18% 7.5 - 8 235 50 14 4.63 23.25 73.05 867.37 -7.62% 8 - 8.5 235 55 14 5.09 24.18 75.95 834.18 -3.50% 8 - 8.5 235 60 14 5.55 25.10 78.86 803.43 0.31% 8 - 8.5 235 65 14 6.01 26.03 81.77 774.88 3.86% 8 - 8.5 235 70 14 6.48 26.95 84.67 748.28 7.16% 8 - 8.5 235 75 14 6.94 27.88 87.58 723.44 10.24% 8 - 8.5 235 80 14 7.40 28.80 90.49 700.21 13.12% 8 - 8.5 245 50 14 4.82 23.65 74.29 852.93 -5.83% 8.5 - 9 245 55 14 5.31 24.61 77.32 819.50 -1.68% 8.5 - 9 245 60 14 5.79 25.57 80.35 788.59 2.16% 8.5 - 9 245 65 14 6.27 26.54 83.38 759.93 5.71% 8.5 - 9 245 70 14 6.75 27.50 86.41 733.28 9.02% 8.5 - 9 245 75 14 7.23 28.47 89.44 708.44 12.10% 8.5 - 9 245 80 14 7.72 29.43 92.47 685.22 14.98% 8.5 - 9 185 50 15 3.64 22.28 70.01 905.07 -12.30% 5.5 - 6 185 55 15 4.01 23.01 72.29 876.42 -8.74% 5.5 - 6 185 60 15 4.37 23.74 74.58 849.54 -5.41% 5.5 - 6 185 65 15 4.73 24.47 76.87 824.25 -2.27% 5.5 - 6 185 70 15 5.10 25.20 79.16 800.42 0.69% 5.5 - 6 185 75 15 5.46 25.93 81.45 777.93 3.48% 5.5 - 6 185 80 15 5.83 26.65 83.73 756.68 6.12% 5.5 - 6 195 50 15 3.84 22.68 71.24 889.36 -10.35% 6 - 6.5 195 55 15 4.22 23.44 73.65 860.24 -6.73% 6 - 6.5 195 60 15 4.61 24.21 76.07 832.96 -3.35% 6 - 6.5 195 65 15 4.99 24.98 78.48 807.36 -0.17% 6 - 6.5 195 70 15 5.37 25.75 80.89 783.29 2.81% 6 - 6.5 195 75 15 5.76 26.52 83.30 760.61 5.63% 6 - 6.5 195 80 15 6.14 27.28 85.71 739.21 8.28% 6 - 6.5 205 50 15 4.04 23.07 72.48 874.18 -8.46% 6.5 - 7 205 55 15 4.44 23.88 75.01 844.63 -4.80% 6.5 - 7 205 60 15 4.84 24.69 77.55 817.02 -1.37% 6.5 - 7 205 65 15 5.25 25.49 80.09 791.15 1.84% 6.5 - 7 205 70 15 5.65 26.30 82.62 766.87 4.85% 6.5 - 7 205 75 15 6.05 27.11 85.16 744.04 7.68% 6.5 - 7 205 80 15 6.46 27.91 87.69 722.52 10.35% 6.5 - 7 215 50 15 4.23 23.46 73.72 859.51 -6.64% 7 - 7.5 215 55 15 4.66 24.31 76.38 829.59 -2.93% 7 - 7.5 215 60 15 5.08 25.16 79.03 801.67 0.53% 7 - 7.5 215 65 15 5.50 26.00 81.69 775.58 3.77% 7 - 7.5 215 70 15 5.93 26.85 84.35 751.13 6.80% 7 - 7.5 215 75 15 6.35 27.70 87.01 728.17 9.65% 7 - 7.5 215 80 15 6.77 28.54 89.67 706.58 12.33% 7 - 7.5 225 50 15 4.43 23.86 74.95 845.33 -4.88% 7.5 - 8 225 55 15 4.87 24.74 77.74 815.07 -1.13% 7.5 - 8 225 60 15 5.31 25.63 80.52 786.90 2.37% 7.5 - 8 225 65 15 5.76 26.52 83.30 760.61 5.63% 7.5 - 8 225 70 15 6.20 27.40 86.08 736.02 8.68% 7.5 - 8 225 75 15 6.64 28.29 88.87 712.97 11.54% 7.5 - 8 225 80 15 7.09 29.17 91.65 691.32 14.22% 7.5 - 8 235 50 15 4.63 24.25 76.19 831.61 -3.18% 8 - 8.5 235 55 15 5.09 25.18 79.10 801.05 0.61% 8 - 8.5 235 60 15 5.55 26.10 82.00 772.65 4.13% 8 - 8.5 235 65 15 6.01 27.03 84.91 746.21 7.41% 8 - 8.5 235 70 15 6.48 27.95 87.82 721.51 10.48% 8 - 8.5 235 75 15 6.94 28.88 90.72 698.39 13.35% 8 - 8.5 235 80 15 7.40 29.80 93.63 676.71 16.04% 8 - 8.5 245 50 15 4.82 24.65 77.43 818.32 -1.53% 8.5 - 9 245 55 15 5.31 25.61 80.46 787.50 2.29% 8.5 - 9 245 60 15 5.79 26.57 83.49 758.92 5.84% 8.5 - 9 245 65 15 6.27 27.54 86.52 732.34 9.14% 8.5 - 9 245 70 15 6.75 28.50 89.55 707.56 12.21% 8.5 - 9 245 75 15 7.23 29.47 92.58 684.40 15.08% 8.5 - 9 245 80 15 7.72 30.43 95.61 662.70 17.77% 8.5 - 9 255 40 15 4.02 23.03 72.36 875.68 -8.65% 9 - 9.5 255 45 15 4.52 24.04 75.51 839.10 -4.11% 9 - 9.5 255 50 15 5.02 25.04 78.66 805.46 0.06% 9 - 9.5 255 55 15 5.52 26.04 81.82 774.41 3.92% 9 - 9.5 255 60 15 6.02 27.05 84.97 745.66 7.48% 9 - 9.5 255 65 15 6.53 28.05 88.13 718.98 10.79% 9 - 9.5 255 70 15 7.03 29.06 91.28 694.13 13.88% 9 - 9.5 265 40 15 4.17 23.35 73.35 863.86 -7.18% 9.5 - 10 265 45 15 4.69 24.39 76.62 826.91 -2.60% 9.5 - 10 265 50 15 5.22 25.43 79.90 792.99 1.61% 9.5 - 10 265 55 15 5.74 26.48 83.18 761.74 5.49% 9.5 - 10 265 60 15 6.26 27.52 86.46 732.86 9.07% 9.5 - 10 265 65 15 6.78 28.56 89.73 706.09 12.39% 9.5 - 10 265 70 15 7.30 29.61 93.01 681.21 15.48% 9.5 - 10 275 40 15 4.33 23.66 74.33 852.36 -5.76% 10 - 10.5 275 45 15 4.87 24.74 77.74 815.07 -1.13% 10 - 10.5 275 50 15 5.41 25.83 81.14 780.90 3.11% 10 - 10.5 275 55 15 5.95 26.91 84.54 749.48 7.01% 10 - 10.5 275 60 15 6.50 27.99 87.94 720.49 10.60% 10 - 10.5 275 65 15 7.04 29.07 91.34 693.66 13.93% 10 - 10.5 275 70 15 7.58 30.16 94.74 668.76 17.02% 10 - 10.5 185 40 16 2.91 21.83 68.57 924.01 -14.65% 5.5 - 6 185 45 16 3.28 22.56 70.86 894.17 -10.94% 5.5 - 6 185 50 16 3.64 23.28 73.15 866.20 -7.47% 5.5 - 6 185 55 16 4.01 24.01 75.44 839.92 -4.21% 5.5 - 6 185 60 16 4.37 24.74 77.72 815.20 -1.15% 5.5 - 6 185 65 16 4.73 25.47 80.01 791.88 1.75% 5.5 - 6 185 70 16 5.10 26.20 82.30 769.87 4.48% 5.5 - 6 195 40 16 3.07 22.14 69.56 910.86 -13.02% 6 - 6.5 195 45 16 3.45 22.91 71.97 880.34 -9.23% 6 - 6.5 195 50 16 3.84 23.68 74.38 851.80 -5.69% 6 - 6.5 195 55 16 4.22 24.44 76.80 825.04 -2.37% 6 - 6.5 195 60 16 4.61 25.21 79.21 799.92 0.75% 6 - 6.5 195 65 16 4.99 25.98 81.62 776.28 3.68% 6 - 6.5 195 70 16 5.37 26.75 84.03 754.00 6.45% 6 - 6.5 205 40 16 3.23 22.46 70.55 898.09 -11.43% 6.5 - 7 205 45 16 3.63 23.26 73.09 866.93 -7.56% 6.5 - 7 205 50 16 4.04 24.07 75.62 837.86 -3.96% 6.5 - 7 205 55 16 4.44 24.88 78.16 810.68 -0.59% 6.5 - 7 205 60 16 4.84 25.69 80.69 785.21 2.58% 6.5 - 7 205 65 16 5.25 26.49 83.23 761.29 5.54% 6.5 - 7 205 70 16 5.65 27.30 85.76 738.78 8.34% 6.5 - 7 215 40 16 3.39 22.77 71.54 885.67 -9.89% 7 - 7.5 215 45 16 3.81 23.62 74.20 853.93 -5.95% 7 - 7.5 215 50 16 4.23 24.46 76.86 824.38 -2.29% 7 - 7.5 215 55 16 4.66 25.31 79.52 796.81 1.14% 7 - 7.5 215 60 16 5.08 26.16 82.18 771.03 4.33% 7 - 7.5 215 65 16 5.50 27.00 84.84 746.86 7.33% 7 - 7.5 215 70 16 5.93 27.85 87.49 724.16 10.15% 7 - 7.5 225 40 16 3.54 23.09 72.53 873.58 -8.39% 7.5 - 8 225 45 16 3.99 23.97 75.31 841.30 -4.38% 7.5 - 8 225 50 16 4.43 24.86 78.09 811.32 -0.67% 7.5 - 8 225 55 16 4.87 25.74 80.88 783.41 2.80% 7.5 - 8 225 60 16 5.31 26.63 83.66 757.35 6.03% 7.5 - 8 225 65 16 5.76 27.52 86.44 732.97 9.06% 7.5 - 8 225 70 16 6.20 28.40 89.23 710.11 11.89% 7.5 - 8 235 40 16 3.70 23.40 73.52 861.83 -6.93% 8 - 8.5 235 45 16 4.16 24.33 76.42 829.05 -2.86% 8 - 8.5 235 50 16 4.63 25.25 79.33 798.67 0.90% 8 - 8.5 235 55 16 5.09 26.18 82.24 770.45 4.41% 8 - 8.5 235 60 16 5.55 27.10 85.14 744.15 7.67% 8 - 8.5 235 65 16 6.01 28.03 88.05 719.58 10.72% 8 - 8.5 235 70 16 6.48 28.95 90.96 696.59 13.57% 8 - 8.5 245 40 16 3.86 23.72 74.51 850.38 -5.51% 8.5 - 9 245 45 16 4.34 24.68 77.54 817.15 -1.39% 8.5 - 9 245 50 16 4.82 25.65 80.57 786.41 2.43% 8.5 - 9 245 55 16 5.31 26.61 83.60 757.91 5.96% 8.5 - 9 245 60 16 5.79 27.57 86.63 731.40 9.25% 8.5 - 9 245 65 16 6.27 28.54 89.66 706.68 12.32% 8.5 - 9 245 70 16 6.75 29.50 92.69 683.57 15.19% 8.5 - 9 255 40 16 4.02 24.03 75.50 839.24 -4.13% 9 - 9.5 255 45 16 4.52 25.04 78.65 805.58 0.05% 9 - 9.5 255 50 16 5.02 26.04 81.81 774.52 3.90% 9 - 9.5 255 55 16 5.52 27.04 84.96 745.77 7.47% 9 - 9.5 255 60 16 6.02 28.05 88.11 719.08 10.78% 9 - 9.5 255 65 16 6.53 29.05 91.27 694.23 13.86% 9 - 9.5 255 70 16 7.03 30.06 94.42 671.04 16.74% 9 - 9.5 265 40 16 4.17 24.35 76.49 828.38 -2.78% 9.5 - 10 265 45 16 4.69 25.39 79.76 794.34 1.44% 9.5 - 10 265 50 16 5.22 26.43 83.04 762.99 5.33% 9.5 - 10 265 55 16 5.74 27.48 86.32 734.02 8.93% 9.5 - 10 265 60 16 6.26 28.52 89.60 707.16 12.26% 9.5 - 10 265 65 16 6.78 29.56 92.87 682.21 15.35% 9.5 - 10 265 70 16 7.30 30.61 96.15 658.95 18.24% 9.5 - 10 275 40 16 4.33 24.66 77.48 817.80 -1.47% 10 - 10.5 275 45 16 4.87 25.74 80.88 783.41 2.80% 10 - 10.5 275 50 16 5.41 26.83 84.28 751.79 6.72% 10 - 10.5 275 55 16 5.95 27.91 87.68 722.63 10.34% 10 - 10.5 275 60 16 6.50 28.99 91.08 695.64 13.69% 10 - 10.5 275 65 16 7.04 30.07 94.48 670.60 16.80% 10 - 10.5 275 70 16 7.58 31.16 97.88 647.30 19.69% 10 - 10.5

I found 175 HR 14s for sale: https://www.longstonetyres.co.uk/175hr14-michelin-xas.html These are 634mm, which makes the ratio for the sidewall 79.542857142% So Arne was right according to this tire.

Right, but several tire retailers list the sidewall ratio of a 175HR14 at 82%, which is 0.55 inches larger in diameter and throws the equation quite significantly. All of these sites have something that supports the 175HR14 sidewall ratio being 82%. https://www.moderntiredealer.com/article/311243/understanding-tire-dimensions https://en.wikipedia.org/wiki/Tire_code https://www.tirerack.com/tires/tiretech/45_conversionchart.jsp (see 1960 to present EURO-METRIC column) https://www.utires.com/articles/buying-tires-guide-tire-numbers-mean/ https://www.errolstyres.co.za/odcalculator https://www.denniskirk.com/learn/tire-sizes-explained If it was 82%, then a 195/70-14 is 0.95 inches smaller in diameter and additional RPM. Ultimately, though, I'm not trying to argue whether people should get 195/70-14s or not. I'm more interested in all the other sizes and which ones are good choices, particularly for 15" rims, but also 16s.

4 hours and counting. The insides of these were black with brake dust and Missouri swamp grunge. I think I’ve figured out the winning combination of degreasers and acids (all aluminum safe), various brushes and elbow grease. Hopefully I’ll have these ready for filing, sanding, and polishing by next weekend.

That's helpful, thanks. I have found various places online that give 82% as the ratio for a 175sr14, but I guess I've seen 78% just as much, and Arne gives the ratio as 80% in that thread you posted. That 4% spread makes a huge difference in what options will work, though, so thanks. The 280Z size I have above came from Arne's post in this thread (#19): From what I understand is the195/70-14 is a common choice to replace the unavailable sizes, not the original size. However, none of this solves the RPM question I had.

Hi everyone, According to some searches I have done the OEM tires for S30s in the USA were: Brand Model Width Ratio Rim Sidewall Diameter Circumference Revs/Mile Difference OEM 240z 175 82 14 5.65 25.30 79.48 797.18 0.00% OEM 280z 197 70 14 5.43 24.86 78.09 811.32 -1.77% I see above that Arne recommended around 825-840 revolutions per mile to keep the speedo accurate, but that doesn't match the math I have above, so either those aren't the right OEM tire sizes or those aren't the right RPM figures. I wonder if Arne's numbers come from pairing them with a different or a-typical transmission speedometer gear. I am putting together a spreadsheet of available tire sizes for 14 and 15" wheels and what to get this correct first. If you know of better threads with more or more accurate information, please reply,y with the link so that we can connect all of this and ensure that people don't go down the wrong path. I know this is a long dead thread, but in an effort to make sure that people are finding the best information possible, I wanted to push on some things said and verify what I have been finding in other places.

That’s how the new ones came. One of the old ones I pulled had one and the other didn’t.

Front legs done. Flowed this: http://atlanticz.ca/zclub/techtips/frontwheelbearings/index.html

I found an Elephant that isn’t on an oil cap: I’ve looked all over and have cannot find any references to Nissan MP Elephant Grease, but there it is, right in the FSM in figure FA-22. Was this real? That would be an interesting piece of memorabilia.

Done. Ran into a few surprises (spacers aren’t relieved for an o-ring so I made a gasket out of Blue RTV, had to press the spacers on with a pile of washers and old hardware) but it was a straight forward mini-job. All torqued down and ready for bearings and discs.

I think Jeep has some very nice colors going right now. They have a nice range of non-metallics that look like updates to some of the Datsun colors, of you are interested in solids. Same with this year’s Hondas. Sent from my iPhone using Classic Zcar Club mobile

Alright! All those holes have been tapped. I started with the largest diameter (easiest) and worked through to the smallest (most difficult) in case the last one needed a drill, which it didn’t. The one in the photo above was the first one, which gave me mostly just rusty sludge and a little coil of por-15 that had dripped into the first few threads. The last one yielded the same rusty sludge plus a bunch of shiny silver metal. Now they are all clean, shiny, and the same size. I can’t find a difference I can’t blame on my micrometer being less than top shelf and my test bolt feels pretty much the same in all of them. I did the brake caliper and dust shield bolts, too, since I was in that mode already.

Problem solved. Ran the tap. Cleaned it out. Ran the bolt. Cleaned it out. Ran the tap. Cleaned it out. It’s bright and shiny and very little damage to the threads. The bolt goes in smoothly but not easily. Feels correct now. I have some new bolts coming to replace this cheep junk.

Yeah, that’s what I’m worried about. I have a time-sert kit waiting to be ordered in case I need to repair them. Here’s the deal with the measurements in millimeters: ZCD’s Stainless Steel bolts: 60.06 long (28.96 grip, 31.1 threads) Strut-base hole depth: 16.04 to 17.55 (top is angled) Front knuckle hole depth: 13.93 Rear knuckle hole depth: 11.6 Spacer hole depth range: 25.83 to 25.04 M12 lock nut thickness: 2.5 New Front Bolt: Min - 16.04t / 41.47gl (57.51mm), Max - 17.55t / 42.26gl (59.81mm) New Rear Bolt: Min - 16.04t / 39.14gl (55.18mm), Max - 17.55t / 39.93gl (57.48mm) I found a place that has 55mm long grade-8 bolts for the rear knuckle holes, although I could just get thicker lock washers. I’m not going to find anything where the grip length and thread lengths are different and I don’t want to cut them, so there are going to be some threads inside of the spacer. If I gets 60mm bolts and let them go all the way through (which looks okay from a quick google image search) I can keep it simple AND put more grip inside the spacers.

The measurements of the hole diameters on my struts from my micrometer are as follows: Left Front: 10.71 Left Rear: 10.68 Right Front: 10.52 Right Rear: 10.43 So not a full MM off, but enough to explain why the 11mm tap went it like it was the right size and why these aftermarket bolts are having a hard time. I’m pretty sure running an m12x1.25 tap through them will solve this.

Not sure of anything, but I didn’t notice any inserts when I inspected them before refinishing them. I used a micrometer on them and I’m starting to think it is poor machining tolerance rather than a totally different size. There’s a very wide range across the four holes. I *might* be able to force a 12mm bolt into the small ones, but I think I’ll just run taps through them to make them even so I don’t break a bolt. The 11mm tap goes in pretty easily, but it’s not sloppy like you would expect from a 1mm diameter difference. ¯\_(ツ)_/¯