In the

    United States Court of Appeals
                 For the Seventh Circuit
                     ____________________
No. 18-2641
DONALD N. TIMM and MARY K. TIMM,
                                                Plaintiffs-Appellants,
                                 v.

GOODYEAR DUNLOP TIRES NORTH AMERICA, LTD.,
an Ohio-based Corporation, et al.,
                                   Defendants-Appellees.
                     ____________________

         Appeal from the United States District Court for the
          Northern District of Indiana, Hammond Division.
             No. 2:14-cv-232 — Philip P. Simon, Judge.
                     ____________________

      ARGUED APRIL 5, 2019 — DECIDED AUGUST 6, 2019
                 ____________________

   Before FLAUM, KANNE, and SCUDDER, Circuit Judges.
    SCUDDER, Circuit Judge. Donald and Mary Timm sustained
serious injuries in a horrific motorcycle accident. Believing de-
fects with the motorcycle and its rear tire caused the acci-
dent—and that their injuries were especially severe because
of a defect with their helmets—the Timms brought a products
liability action under Indiana law against numerous defend-
ants involved in the sale and manufacture of the motorcycle,
2                                                   No. 18-2641

its rear tire, and the helmets they wore at the time of the acci-
dent. Concluding that the Timms failed to present admissible
expert testimony to support their claims, the district court en-
tered summary judgment for the defendants. We affirm.
                                I
    On July 10, 2013, Donald and Mary Timm set off on a
cross-country trip on their Harley-Davidson Ultra Classic.
The Timms intended to drive from their home in Dyer, Indi-
ana to Salt Lake City, Utah. While crossing Nebraska, the cou-
ple suffered a catastrophic accident when the motorcycle’s
rear tire sustained a puncture and rapidly deflated, leading
Donald to lose control of the motorcycle and crash into a con-
crete median barrier. Mary flew off the motorcycle while Don-
ald remained attached to the bike as it slid along the highway.
Though both riders were wearing helmets, each sustained se-
rious head injuries. In addition to suffering a traumatic brain
injury, Donald sustained facial fractures and a cervical spine
injury.
    A few months later, the Timms received notice that the
helmets they were wearing at the time of the accident—Ultra
Low Profile Outlaw Motorcycle Half Helmets—were recalled.
The Timms purchased the helmets two years earlier. Mary
purchased her helmet through a website called Leath-
erUp.com (owned by Nanal, Inc.). Donald purchased his hel-
met through a different internet retailer, which is not a party
to this suit. A company named Tegol imported and distrib-
uted both helmets. In its recall notice, Tegol explained that the
Outlaw helmets failed to conform to certain Department of
Transportation standards and warned that riders “may not be
adequately protected in the event of a crash.”
No. 18-2641                                                    3

    The Timms then brought a products liability action
against Tegol, Nanal, and fourteen other corporate and indi-
vidual defendants involved in the manufacture, distribution,
and sale of Outlaw helmets (which we will collectively call the
helmet defendants). Advancing claims under the Indiana
Products Liability Act, the Timms alleged that their injuries
would have been less severe had their helmets complied with
federal safety standards and that the helmet defendants were
negligent in their recall efforts. The Timms also asserted
claims against Harley-Davidson, the motorcycle manufac-
turer, and Goodyear Dunlop (now known as Sumitomo Rub-
ber USA), the tire manufacturer, contending that defects in the
motorcycle and rear tire caused the accident.
    Beginning with their helmets, the Timms pressed several
claims, including design defect and manufacturing defect. To
show that the helmets enhanced their injuries, the Timms em-
phasized the recall as well as the sheer severity of the injuries
they sustained in the accident. But they did not present any
expert testimony to show that, because of a defect with their
helmets, their injuries were worse than they otherwise would
have experienced in such a severe motorcycle crash. This
omission, the district court concluded, was fatal to their
claims because “a lay juror would not be able to distinguish
between the injuries caused by the motorcycle accident and
the enhanced injuries caused by the alleged defect in the hel-
mets without engaging in speculation.”
    This conclusion, the district court reasoned, found support
in the fact that the helmet defendants offered their own med-
ical expert, who opined that the Timms’ injuries were the type
he would expect following such a serious motorcycle acci-
dent, even if they had been wearing helmets that complied
4                                                 No. 18-2641

with all safety standards. The court accordingly entered sum-
mary judgment in favor of the helmet defendants on the
Timms’ manufacturing and design defect claims. The court
also entered judgment for the defendants on the Timms’
claims alleging negligent recall and failure to comply with
federal safety standards, concluding that the Indiana Prod-
ucts Liability Act permits neither claim.
    Turning to the allegations against Harley-Davidson and
Goodyear, the Timms asserted that the motorcycle’s rear tire
(a Dunlop D402 tire) was defective and unreasonably danger-
ous because, following a puncture, it allowed for both exces-
sive air leakage and the tire to unseat—or come free—from its
rim. These defects, they maintained, caused Mr. Timm to lose
control of the motorcycle and crash. The Timms further al-
leged that the motorcycle itself was defectively designed be-
cause it lacked a tire pressure monitoring system, which
would have alerted Donald to the sudden loss of air in the tire
before he lost control. To support these claims, the Timms
proposed two experts: William Woehrle, a tire specialist, and
Dr. Daniel Lee, an accident reconstructionist. In his report,
Woehrle opined on how and when the tire became unseated
from the rim and the need for a tire pressure monitoring sys-
tem. Dr. Lee likewise sought to testify about the ultimate
cause of the accident and to share his opinion that every mo-
torcycle should be equipped with a tire pressure monitoring
system.
    Harley-Davidson and Goodyear filed motions to exclude
Woehrle’s and Lee’s opinions, arguing they lacked the relia-
bility required by Federal Rule of Evidence 702 and Daubert v.
Merrell Dow Pharmaceuticals, Inc., 

(1993). Follow-
ing a hearing, the district court agreed. The court concluded
No. 18-2641                                                    5

that Woehrle’s opinion that manufacturing defects caused the
tire to unseat from the rim upon being punctured “appear[ed]
to be based on nothing more than his subjective belief and un-
supported speculation,” and thus “fail[ed] to adhere to any of
the Daubert guideposts.” The court also excluded Woehrle’s
opinion on the tire pressure monitoring system, reasoning
that while Woehrle had expertise with respect to tires, he
lacked qualifications related to motorcycles more generally.
The district court judge also determined that Woehrle’s opin-
ions failed to comport with Rule 702 “because they [were] not
based on scientifically valid methodologies.”
   The court similarly excluded Dr. Lee’s testimony, finding
that he lacked tire-related qualifications, and, in any event, his
methodology with respect to both the tire defects and the tire
pressure monitoring system lacked the reliability required by
Daubert.
    Without expert testimony to support any of their claims,
the court granted summary judgment for all defendants on all
of the Timms’ claims.
                               II
   The Timms challenge the district court’s conclusions re-
garding the need for expert testimony on their helmet claims
and the adequacy of their proposed expert testimony for their
motorcycle and tire claims.
                               A
    We begin with the helmet claims. While the Timms ini-
tially sued more than a dozen defendants, by summary judg-
ment, only one corporate defendant remained—Nanal, Inc.
Recall that Nanal owns and operates the website where Mary
Timm purchased her helmet. Because Donald Timm
6                                                   No. 18-2641

purchased his helmet on a different website, and thus not
from a supplier named as a defendant, we consider the helmet
claims only with respect to Mary.
    The parties agree that the Indiana Products Liability Act
governs the Timms’ claims. See Ind. Code § 34-20-1-1. Under
the Act, “a plaintiff must prove that a product was placed into
the stream of commerce in a defective condition unreasonably
dangerous to the user and that plaintiff's injuries were caused
by this dangerous product.” Campbell Hausfeld/Scott Fetzer Co.
v. Johnson, 

, 956 (Ind. 2018).
    The Timms contend that Mary’s helmet was unreasonably
dangerous within the meaning of the Act due to design and
manufacturing defects and a related failure to warn. To sur-
vive summary judgment under each of these theories, Indiana
law required the Timms to show that the alleged defects prox-
imately caused Mary’s injuries. See Piltch v. Ford Motor Co.,

, 632 (7th Cir. 2015) (citing Ford Motor Co. v. Rush-
ford, 

, 810 (Ind. 2007)). The Timms sought to do
so by invoking the doctrine of “crashworthiness,” an ap-
proach to causation that “expands the proximate cause re-
quirement to include enhanced injuries” caused by a defective
product. Green v. Ford Motor Co., 

, 793–94 (Ind.
2011) (quoting Miller v. Todd, 

, 1142 (Ind.
1990)). Put another way, the doctrine applies to situations
where, as here, the allegedly defective product did not cause
the initial accident and any and all resulting injuries, but ra-
ther increased or enhanced the severity of a plaintiff’s injuries.
See 

contend that Mary’s injuries from the crash
were more severe than they would have been had her helmet
met all federal safety regulations. To show that defects in the
No. 18-2641                                                     7

helmet enhanced her injuries, the Timms presented the dis-
trict court with her medical records. While this evidence cer-
tainly confirmed that Mary suffered very serious head injuries
in the accident, we agree with the district court that the rec-
ords alone failed to distinguish those injuries that would have
resulted from any similar crash from any specific enhanced
injuries Mary sustained as a result of the allegedly defective
helmet. While plaintiffs are not always required to provide
expert testimony to establish proximate causation, see U–Haul
Int’l., Inc. v. Nulls Machine & Mfg. Shop, 

, 285 n.3
(Ind. Ct. App. 2000), the district court correctly concluded that
Indiana law required expert testimony here because distin-
guishing expected from enhanced injuries was an inquiry be-
yond the understanding of lay jurors, see 

.
    The district court’s reasoning finds sound support in our
caselaw. We have previously held that when a plaintiff seeks
under Indiana law to distinguish between ordinary and en-
hanced injuries, expert testimony is necessary to prevent the
jury from engaging in guesswork. 

In Piltch v. Ford
Motor Co., for example, the plaintiffs brought manufacturing
and design defect claims under the Indiana Products Liability
Act related to the air bags’ failure to deploy in a car accident.
See 

the plaintiffs failed to present expert testi-
mony as to their injuries, we affirmed summary judgment in
favor of the car manufacturer, explaining that without any ex-
pert testimony, a “lay juror could not distinguish between the
injuries caused by the collision and the enhanced injuries
caused by the air bags' failure to deploy without engaging in
pure speculation.” 

18-2641

    All agree that Mary Timm suffered severe injuries. But
without the assistance of an expert, a juror would be unable
to distinguish between those injuries caused by the crash—in
other words, the injuries anyone in this type of accident
would have suffered—and any enhanced or more severe in-
juries caused by the defective helmet. Summary judgment
was therefore proper on the Timms’ design defect and manu-
facturing defect claims.
    For the sake of completeness, we address the failure-to-
warn claim the Timms advanced based on allegations that the
defendants delayed issuing the helmet recall notice. The dis-
trict court considered this a claim of negligent recall and en-
tered summary judgment for the helmet defendants because
it found no support for such claims under Indiana law. Be-
cause the Timms do not address this argument on appeal, we
consider it waived. See Mahaffey v. Ramos, 

, 1146
(7th Cir. 2009) (declining to consider claims not adequately
briefed).
                               B
    The Timms next argue that summary judgment against
Harley-Davidson and Goodyear was improper because the
district court erred in excluding the testimony of their experts,
William Woehrle and Dr. Daniel Lee.
    At the time of the accident, the Timms were traveling cross
country on their 2006 Harley-Davidson Ultra Classic Motor-
cycle. It is undisputed that the rear tire—manufactured by
Goodyear Dunlop and branded with the name Harley-Da-
vidson—was punctured by a road hazard and began to de-
flate, eventually unseating from its rim. The issue at the heart
of the Timms’ claims requires pinpointing exactly when the
No. 18-2641                                                   9

rubber unseated from the rim. For their part, the Timms con-
tend that the tire’s unseating occurred nearly instantly be-
cause of defects and, in turn, that the unseating caused Don-
ald to lose control of the motorcycle and crash. The defend-
ants urge a contrary view. They resist that the unseating im-
mediately followed the puncture and instead maintain that
the motorcycle crash itself is what caused the tire to unseat
from the rim. The Timms rightly recognized that answering
this causation question required expert testimony. Toward
that end, they offered the opinions of Woehrle and Lee, which
the district court ultimately excluded.
    Federal Rule of Evidence 702 and Daubert govern the ad-
missibility of expert testimony. Under this framework, a trial
judge, as a gatekeeping matter, is responsible for ensuring
that proposed expert testimony “is not only relevant, but reli-
able.” 

. In assessing reliability, “the
role of the court is to determine whether the expert is qualified
in the relevant field and to examine the methodology the ex-
pert has used in reaching his conclusions.” Smith v. Ford Motor
Co., 

, 718 (7th Cir. 2000).
    Although reliability must be assessed case by case, Daubert
identified a non-exhaustive list of factors to aid the analysis.
Relevant considerations include not only whether the expert’s
theory “can be (and has been) tested,” but also whether it has
been “subjected to peer review and 

. Other potential considerations include “the known or po-
tential rate of error” and whether the theory or technique has
achieved “general acceptance” in the relevant expert commu-
nity. 

No one factor is dispositive, however, and
“the Supreme Court has repeatedly emphasized [that] the
Rule 702 test is a flexible one.” 

. The
10                                                    No. 18-2641

Court has likewise underscored that the correct inquiry fo-
cuses not on “the ultimate correctness of the expert’s conclu-
sions,” but rather on “the soundness and care with which the
expert arrived at her opinion.” Schultz v. Akzo Nobel Paints,
LLC, 

, 431 (7th Cir. 2013) (citing 

).
    Faced as we are here with a challenge to a district court’s
exclusion of expert testimony, our review proceeds in two
steps. We “review de novo whether a district judge has fol-
lowed Rule 702 and Daubert” and, if the court correctly “ap-
plied the Rule 702/Daubert framework, we [then] review [its]
decision to admit or exclude expert testimony for abuse of dis-
cretion.” Haley v. Kolbe & Kolbe Millwork Co., 

, 611
(7th Cir. 2017).
    We find no errors here. In response to the defendants’ mo-
tions to exclude Woehrle’s and Lee’s testimony, the district
court held a Daubert hearing. The court used the hearing to
probe Woehrle about the basis for his opinions, the method-
ology he employed to formulate his theories, and the poten-
tial rate of error of his approach—all proper considerations
under Rule 702 and Daubert. In its written decision, the court
further conveyed its understanding of the Rule and Daubert
factors by accurately articulating them and proceeding to ap-
ply them to Woehrle’s and Lee’s testimony and opinions. See
Clark v. River Metals Recycling, 

, 438 (7th Cir. 2019).
There is no question the district court applied the correct evi-
dentiary framework.
    Turning to the court’s rulings, we see no abuse of discre-
tion with the exclusion of Woehrle’s and Lee’s testimony. In
his report and testimony, Woehrle posited that the Timms’
motorcycle accident was the result of the tire unseating from
No. 18-2641                                                   11

its rim. He further opined that the unseating occurred because
there was excess “flash” in the bead area (the edge of the tire
that sits on the wheel rim) and insufficient rubber covering
the chafer strip (a reinforcement of the bead area), which
weakened the fit between the tire and the rim. Woehrle testi-
fied that he arrived at this conclusion by conducting a physi-
cal examination of the tire and wheel. When pressed about his
methodology, however, Woehrle conceded that he could
point to no empirical data or controlled experiments to sup-
port his opinions. He further acknowledged that he had not
done any testing to validate his opinion, was unaware of any
relevant tests conducted by others, and knew of no way others
could objectively replicate his approach.
    On this evidence, the district court was well within its dis-
cretion to exclude Woerhle’s opinions about the cause of the
tire unseating. To satisfy the requirements of Rule 702 and
Daubert, Woerhle needed to show that his conclusions were
the fruit of a rigorous, objectively-verifiable approach—some-
thing more than mere speculation. While Woerhle may well
have had the experience and knowledge to make this show-
ing, he failed to do so. All of this leads to underscore anew
that even a “supremely qualified expert cannot waltz into the
courtroom and render opinions unless those opinions are
based upon some recognized scientific method.” 

(quoting Clark v. Takata Corp., 

, 759 n.5
(7th Cir. 1999)). The record amply supports the district court’s
conclusion that the Timms failed to establish that Woehrle’s
opinions were sufficiently reliable.
   Nor do we see any abuse of discretion in the district
court’s exclusion of Dr. Lee’s opinions regarding the cause of
the crash. In his report, Dr. Lee opined that Mr. Timm lost
12                                                No. 18-2641

control of the motorcycle because the rear tire started to
“hop.” This hopping, Lee maintained, was the result of the
tire unseating from the rim. In addition to questioning Lee’s
qualifications with respect to the functioning of tires and how
they can unseat from a rim, the district court concluded that
Lee’s methodology did not comport with Daubert because Lee
failed to point to any test replicating the conditions under
which the rubber beading would have come unseated or any
testing to support his theory that bead unseating would cause
a motorcycle to hop. Lee likewise failed to identify any scien-
tific literature to support his opinion. In the absence of any-
thing to support his conclusions, the district court acted
within its discretion in excluding Dr. Lee’s opinions about the
cause of the unseating.
    Finally, we consider the court’s exclusion of Woehrle’s
and Lee’s testimony regarding the tire pressure monitoring
system. The Timms alleged that the motorcycle was defec-
tively designed because it should have been equipped with
such a monitoring system. They sought to support this claim
with testimony from both Woehrle and Lee, who opined that
the accident would not have happened if the motorcycle came
equipped with such a system.
    The district court concluded that neither expert possessed
the requisite qualifications to offer such testimony. Here, too,
we find no abuse of discretion. Though Woehrle has expertise
with the design and operation of tires, the record supports the
district court’s conclusion that this knowledge and experience
does not extend to motorcycles. Indeed, Woehrle himself
acknowledged that he is not an expert in the design of tire
pressure monitoring systems for motorcycles and he has
never conducted any research on this topic. While the court
No. 18-2641                                                  13

recognized that Dr. Lee did have significant experience with
motorcycles, Lee testified during his deposition that he lacked
familiarity with tire pressure monitoring systems. Given this
admission, the district court’s assessment of Lee’s qualifica-
tions—and its decision to exclude his testimony—reflected no
abuse of discretion.
    Because the Timms’ manufacturing and design defect
claims against Harley-Davidson and Goodyear rested on
Woehrle’s and Lee’s testimony, the district court’s evidentiary
rulings defeated those claims. The same evidentiary shortfalls
defeated the Timms’ claim based on a failure to warn.
                             * * *
   What happened here was tragic. Donald and Mary Timm
suffered extremely serious injuries in an extremely serious
motorcycle accident. We have no doubt that these injuries
have impacted their lives in substantial and lasting ways.
What we cannot say, though, is that the district court commit-
ted any error in rejecting their legal claims. So we are left to
AFFIRM.