From: BRANDT_JOBST/HP1900_01@HPLOMG.HPL.HP.COM
Newsgroups: rec.bicycles
Subject: Re: request tire pres v rolling resistance chart
Date: 1 Sep 92 17:20:16 GMT

This should not go into the FAQ but I have some data taken a while
back that is representative of typical tires even today.   These
do not include off road tires because such information did not
interest the effort at that time.  Such information will be collected
in the near future.  The values in these files were collected by IRC
on steel drum tire machines commonly used by tire companies.  The
work was done for Avocet who published these as curves on a common
graph that showed relative RR values at various inflation pressures.

For those who bother to graph the values (grams force)/(kg/cm pressure)
and use a power fit curve, will see that as tire casings get thinner and
tread and tube get thinner, the effect of inflation pressure is reduced.
That is to say flexing a coarse cord heavy tire due to low pressure is
far worse than doing the same with a light weight racing tire.  Tires
with the lowest RR are also the least affected by inflation pressure.

In that respect, the two tubulars listed are shifted up above lesser tires
because the rim glue eats up a constant drag regardless of inflation
pressure.  This difference points up the reason for hardening rim glue
that was used by track racers in the past.  It was said by those who
didn't know better that track glue (tipo pista) was for safety reasons
but in fact it was to minimize RR for such things as the pursuit and
other events where 1/100 seconds count.  From these curves it also
becomes evident that although tubulars sound good, their RR is not as
good as a good clincher unless glued with shellac type hard glue.

jobst_brandt@hplabs.hp.com

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Item Subject: Tires 25C
AVO 700x25C & 27x1, SBI 700x21C & 27x7/8 Tires (smooth tread)
Rolling resistance (g) vs. inflation pressure (kg/cm2) @ 50 kg load
Col  1 - Inflation Pressure (kg/cm2)
Col  2 - S Ultra Light/R  27x7/8 A
Col  3 - S Ultra Light/R  27x7/8 B
Col  4 - S Turbo/R        27x7/8 A
Col  5 - S Turbo/R        27x7/8 B
Col  6 - Avocet 30        27x1   A
Col  7 - Avocet 30        27x1   B
Col  8 - Avocet 20        27x1   A
Col  8 - Avocet 20        27x1   B
Col 10 - S Turbo/R       700x21C A
Col 11 - S Turbo/R       700x21C B
Col 12 - S Ultra-light/R 700x21C C
Col 13 - S Ultra-light/R 700x21C D
Col 16 - Avocet 20       700x25C A
Col 17 - Avocet 20       700x25C B
Col 15 - Avocet 30       700x25C A
Col 14 - Avocet 30       700x25C B
 c1  c2  c3  c4  c5  c6  c7  c8  c9 c10 c11 c12 c13 c14 c15 c16 c17
3.5 431 426 432 430 408 412 400 410 433 432 413 412 443 453 417 400
4.0 381 380 385 375 362 374 372 380 390 381 377 363 396 410 384 368
4.5 344 344 349 345 335 345 343 358 360 351 352 332 372 384 341 340
5.0 318 323 328 317 311 321 328 340 333 327 313 308 347 357 320 316
5.5 303 303 308 299 295 301 310 322 312 305 293 286 327 333 303 295
6.0 286 287 289 279 280 286 293 308 293 289 279 269 315 316 290 280
6.5 275 274 272 269 270 278 283 299 280 277 261 255 298 300 274 266
7.0 262 265 261 260 261 269 272 288 267 264 253 242 290 290 261 255
7.5 252 256 253 247 252 258 269 277 259 253 243 232 279 278 249 247
8.0 245 248 244 240 243 249 264 272 250 244 234 222 272 271 243 239
8.5 236 240 236 232 237 245 259 261 241 236 226 217 265 263 237 233
9.0 233 237 231 228 235 241 256 257 237 234 221 211 264 262 235 228

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Item Subject: Tires 28C

700x25C, 700x28C Tires and Vitoria and Clement Tubulars
Rolling resistance (g) vs. inflation pressure (kg/cm2) @ 50 kg load
Col  1 - Inflation Pressure (kg/cm2)
Col  2 - S Touring         700x25C
Col  3 - S Touring II      700x25C
Col  4 - S Ultra L         700x25C
Col  5 - S Turbo           700x25C
Col  6 - M HiLite Comp     700x20C
Col  7 - Avocet 20         700x25C
Col  8 - Avocet 30         700x25C
Col  9 - Vittoria CX       Tublr
Col 10 - Clement Seta 250  Tublr
Col 11 - S Touring         700x28C
Col 12 - S Turing II       700x28C
Col 13 - S Turbo           700x28C
Col 14 - M HiLite          700x23C
Col 15 - Avocet 20         700x28C
Col 16 - Avocet 30         700x28C
 c1  c2  c3  c4  c5  c6  c7  c8  c9 c10 c11 c12 c13 c14 c15 c16
3.5 576 531 480 444 493 421 417 423 408 531 521 508 434 390 384
4.0 522 483 437 408 440 390 377 398 385 484 472 453 389 360 356
4.5 483 441 399 378 399 365 343 380 366 451 433 415 358 340 331
5.0 452 408 373 353 374 345 326 362 351 423 403 388 339 322 311
5.5 427 379 351 334 350 327 309 348 339 403 381 369 320 307 296
6.0 402 359 334 316 330 312 293 336 330 384 362 351 302 295 283
6.5 379 340 320 301 311 299 281 327 321 370 347 334 287 284 270
7.0 362 324 309 287 296 285 270 321 314 357 333 322 277 274 260
7.5 348 313 297 277 281 274 260 317 307 344 321 311 267 267 250
8.0 335 301 286 267 270 267 254 311 302 335 312 302 260 259 243
8.5 323 294 280 261 259 260 248 306 294 329 305 295 254 252 238
9.0 312 285 273 255 256 256 242 305 289 323 300 290 249 248 234